The Pulpit Commentary
Form an introduction to the Hebrew code of prohibited degrees of marriage and of forbidden sins of lust. The formal and solemn declaration, I am the Lord your God, is made three times in these five verses. This places before the people the two thoughts:

1. That the Lord is holy, and they ought to be like him in holiness;

2. That the Lord has commanded holiness, and they ought to obey him by being holy. Because the Lord is their God, and they are his people, they are, negatively, to refrain from the vicious habits and lax customs prevalent in the land of Egypt wherein they dwelt, and in the land of Canaan whither they were going, the sensuality of which is indirectly condemned by the injunctions which command purity in contrast to their doings; and, positively, they are to keep God's statutes, and his judgments, as laid down in the following code, which if a man do, he shall live in them. The latter clause is of special importance, because it is repeated in the same connection by Ezekiel (Eze_20:11, Eze_20:13, Eze_20:21), and in the Levitical confession in the Book of Nehemiah (Neh_9:29), and is quoted by St. Paul in a controversial sense (Rom_10:5; Gal_3:12). Its full meaning is that by obedience to God's commands man attains to a state of existence which alone deserves to be called true life—"the life which connects him with Jehovah through his obedience" (Clark). And this involves the further truth that disobedience results in death. Accordingly, St. Paul uses the text as being the testimony of the Law with regard to itself, that salvation by it is of works in contrast with faith. (Cf. Luk_10:28.) We have no evidence to tell us what were the doings of the land of Canaan in respect to the marriage relation, but this chapter is enough to show that the utmost laxity prevailed in it, and we may be sure that their religious rites, like those of Midian (Num_25:1-18), were penetrated with the spirit of licentiousness. With regard to the doings of the land of Egypt, we have fuller information. We know that among the Egyptians marriage with sisters and half-sisters was not only permissible, but that its propriety was justified by their religious beliefs, and practiced in the royal family (Died. Sic; 1:27; Die. Cass; 42). Other abominations condemned in this chapter (verse 23) also, as we know, existed there (Herod; 2:46), and if queens could be what in later times Cleopatra was, we may imagine the general dissoluteness of the people. Among Persians, Medes, Indians, Ethiopians and Assyrians, marriage with mothers and daughters was allowed, and from the time of Cambyses, marriage with a sister was regarded as lawful (Herod; Neh_3:31). The Athenians and Spartans permitted marriage with half-sisters. All these concessions to lust, and ether unclean acts with which the heathen world was full (verse 22; Rom_1:27), were fallings away from the law of purity implanted in the heart of man and now renewed for the Hebrew people.

Unknown

The next thirteen verses contain the law of incest, or the prohibited degrees of marriage. The positive law of marriage, as implanted in the human heart, would be simply that any man of full age might marry any woman of full age, provided that both parties were willing. But this liberty is at once controlled by a number of restrictions, the main purpose of which is to prevent incest, which, however much one nation may come to be indifferent to one form of it, and another to another, is yet abhorrent to the feelings and principles of mankind. The Hebrew restrictive law is contained in one verse. None of you shall approach to any that is near of kin to him to uncover their nakedness: I am the Lord. All that follows (Lev_18:9-18) is simply an amplification and an explanation of the words, near of kin to him. These words would be literally rendered, flesh of his flesh, or less probably, remainder of his flesh. They certainly include within the compass of their meaning those that are near by affinity, as much as those that are near by consanguinity. This is proved by the instances given below, where no difference is drawn between blood relations and relations by marriage, the latter being supposed to become the former, in consequence of the marriage that has taken place. Nearness of kin is generally counted by "degrees;" but, unfortunately, this word is itself ambiguous, for it is used in different senses by canonists and by civilians. So far as the direct line is concerned, the same method of calculation is observed by the canon and by the civil law. There is one degree from the son to the mother, two degrees to the grandmother; one degree from the father to the daughter, two degrees to the granddaughter. But this is not so with the collateral lines. A brother and sister, for example, are regarded by the canon law as in the first degree of kinship, because there is only one step to the father, in whom their blood meets; but the civil lawyers consider them as being in the second degree, because, as they calculate, there is one step from the brother to the father, and a second from the father to the sister. An aunt is, according to the canonists, in the second degree of propinquity, because there are two steps from her nephew to his grandfather, who is likewise her father, in whom their blood unites; but, according to the civilian's calculation, there are three steps, namely, from her nephew to his grandfather, two steps, and a third from that grandfather to his daughter the aunt; and therefore the aunt and nephew are in the third degree of propinquity. The case of an uncle and niece is exactly the same as that of a nephew and aunt. On the same principle, according to the canonists, first cousins are in the second degree of kinship; according to the civilians, in the fourth. Propinquity by affinity is calculated in just the same way; so that the brother's wife is in the same degree of relationship as the brother, and wife's sister as the sister by blood. In the code before us, confirmed by that in Deuteronomy, marriage is forbidden with the following blood relations: mother (verse 7), daughter (verse 17), sister (verse 9; Le Deu_20:17; Deu_27:22), granddaughter (verse 10), aunt (verses 12, 13; Le Deu_20:19); and with the following relations by affinity: mother-in-law (verse 17; Deu_20:14; Deu_27:23), daughter-in-law (verse 15; Le Deu_20:12), brother's wife (verse 16; Le 20:21), stepmother (verse 8; Deu_20:11; Deu_22:30; see Gen_49:4; 1Co_5:1), stepdaughter and step-granddaughter (verse 17), uncle's wife, or aunt by marriage (verse 14; Le Deu_20:20); putting aside for the present the question of who is meant by a wife to her sister, in verse 18. In these lists, according to the canonists' method of reckoning, the mother, the daughter, and the sister are related in the first degree of consanguinity; the wife's mother, the wife's daughter, the stepmother, the daughter-in-law, the brother's wife, are related in the first degree of affinity. The granddaughter and the aunt are in the second degree of consanguinity; the wife's granddaughter and the uncle's wife in the second degree of affinity. According to the civilians' reckoning, the following would be the degrees of propinquity:—The mother and the daughter would be in the first degree of consanguinity; the wife's mother, the wife's daughter, the stepmother, the daughter-in-law, would be in the first degree of affinity. The sister and the granddaughter would be in the second degree of consanguinity; the brother's wife and the wife's granddaughter would be in the second degree of affinity. The aunt by blood would be in the third degree of consanguinity, and the uncle's wife, or aunt by marriage, would be in the third degree of affinity. The wife's sister, with regard to whom it is questioned whether she is referred to or not in verse 18, is in the first degree of affinity (a man's wife being regarded as himself) according to the canonists' reckoning, and in the second according to the civilians'. There is no mention made in the code of the grandmother, the niece, and the cousin-german. All of these are in the second degree of consanguinity according to the canon law; and according to the civil law, the grandmother would be in the second degree, the niece in the third, and the cousin-german in the fourth. It may reasonably be supposed that by the expression, None of you shall approach to any that is near of kin to him, to uncover their nakedness, intercourse is forbidden between all those who are related by consanguinity or affinity in the first and second degrees according to the canonists' reckoning (except cousins-german, whose case is considered below); in the first, second, and third degrees 'according to the civilians' method of calculating; whether they are mentioned by name in the list or not. It is only by implication, not by direct injunction, that marriage even with a daughter is forbidden (verse 17).

Lev_18:7, Lev_18:8

Incest with a stepmother is placed next after that with a mother. On account of the unity caused by marriage ("they shall be one flesh," Gen_2:24), the stepmother's nakedness is the father's nakedness. The tie of affinity is thus declared to be similar in its effects to the tie of consanguinity. Reuben's sin, by which he forfeited his birthright, is connected with this offense, but is of a more heinous character, as his father was alive at the time of his transgression (Gen_49:4). It is one of the sins which Ezekiel enumerates as those which brought the judgment of God on Israel (Eze_22:10). "That one should have his father's wife" is declared by St. Paul to be "such fornication as is not named among the Gentiles," and to call for the excommunication of the offender (1Co_5:1-5). Adonijah's marriage with Abishag, so strongly resented by Solomon on political grounds, is not denounced as morally reprehensible, probably because Abishag was not the wife of David in such a way as to cause the marriage with his son to be abominable in the eye of the law (cf. 1Ki_1:4 with Amo_2:7). Absalom's" going in unto his father's concubines" was regarded as the final act which made reconciliation with his father impossible (2Sa_16:22; 2Sa_20:3). The history of the Church has shown that marriage with the stepmother has had to be again and again prohibited by Council after Council (see Smith and Cheetham's 'Dictionary of Antiquities,' s.v. 'Prohibited Degrees').

The Pulpit Commentary
In the third place, incest with a sister is forbidden, and it is specifically stated that under the term "sister" is meant the half-sister, the daughter of thy father, or … thy mother,… born at home, as would naturally be the case if she were the father's daughter, or born abroad, that is, the daughter of the mother by a previous marriage, when she belonged to a different household. Tamar's appeal to Amnon, "I pray thee speak unto the king; for he will not withhold me from thee," exhibits to us the poor woman grasping at any argument which might save her from her half-brother's brutality, and does not indicate that such marriages were, in the time of David, permissible (2Sa_13:29). The exact degree of relationship which existed between Abraham and Sarah is not altogether certain (cf. Gen_20:12 with Gen_11:29). Ezekiel reckons this sin in the catalogue of the iniquities of Jerusalem (Eze_22:11).

The Pulpit Commentary
The fourth case of incest which is prohibited is that with a granddaughter, whether the daughter of son or daughter, for, as they are descended from the grandfather, their's is thine own nakedness.

The Pulpit Commentary
Incest with a half-sister on the father's side is again forbidden. Perhaps "the prohibition refers to the son by a first marriage, whereas Lev_18:9 treats of the son by a second marriage" (Keil).

The Pulpit Commentary
Fifthly, incest with a paternal or maternal aunt is forbidden; sixthly, with an aunt by marriage; seventhly, with a daughter-in-law. The last of these finds its place in Ezekiel's catalogue of abominations (Eze_22:11; cf. Gen_28:18, 26).

The eighth ease of incest is intercourse with a brother's wife. Yet this is commanded under certain circumstances in the Book of Deuteronomy, and was practiced in patriarchal times (Gen_38:8). The following are the circumstances under which it is commanded. "If brethren dwell together, and one of them die, and have no child, the wife of the dead shall not marry without unto a stranger: her husband's brother shall go in unto her, and take her to him to wife, and perform the duty of an husband's brother unto her" (Deu_25:5). It has been asked, "How can the same thing be forbidden as immoral in Leviticus, and commanded as a duly in Deuteronomy?" Bishop Wordsworth replies, "In a special case, for a special reason applicable only to the Jews, God was pleased to dispense with that law, and in the plenitude of his omnipotence to change the prohibition into a command.… God cannot command anything that is sinful. For sin is 'transgression of the Law' (1Jn_3:4), and whatever he commands is right. But it would be presumptuous to say that we may dispense with God's law concerning marriage, because he in one case dispensed with it; as it would be impious to affirm that murder is not immoral, and may be committed by us, bemuse God, who is the sole Arbiter of life and death, commanded Abraham to slay his son Isaac." The levirate marriage was not a concession to the desires of the second brother, but a duty enjoined for a family or tribal purpose, and it was plainly at all times must distasteful. Thus Onan refused to perform his duty to Er's wife (Gen_38:9); the legislation in Deuteronomy anticipates objection on the part of the brother, and institutes an in-suiting ceremony to be gone through by him if he declines to do his duty to his dead brother (Deu_25:9, Deu_25:10), which we see carried out in some of its details in the case of Ruth's kinsman (Rth_4:7, Rth_4:10). Indeed, in such a marriage, the second husband seems rather to have been regarded as the continuation of the first husband than as having a substantive existence of his own as a married man. He performed a function in order "that the name of his brother which is dead may not be put out of Israel" (Deu_25:6), "to raise up the name of the dead upon his inheritance, that the name of the dead be not cut off from among his brethren" (Rth_3:10). The second husband's position may be compared to that of the concubine presented by Rachel to her husband. "Behold my maid Bilhah, go in unto her; and she shall bear upon my knees, that I may also have children by her" (Gen_30:3). The whole object of the rule was that, as the elder brother could not keep up the flintily by begetting an heir, the younger brother should do it for him after his death.

The Pulpit Commentary
The ninth form of incest prohibited is intercourse with a stepdaughter, or step-granddaughter, or mother-in-law. The expression made use of, Thou shalt not uncover the nakedness of a woman and her daughter, covers the case of a man's own daughter, and it is singular that it is only in this incidental manner that it is specifically named. But it has been already disposed of by the general command, None of you shall approach to any that is near of kin to him, to uncover their nakedness. The daughter being nearest of kin, this command was sufficient without further specification. The niece and probably the wife's sister are forbidden by the same general rule (see following note).

The Pulpit Commentary
Neither shalt thou take a wife to her sister, to vex her, to uncover her nakedness, beside the other in her life time. Do these words refer to the marriage of two sisters or not? It has been passionately affirmed that they do, by those who are opposed to permission being granted for marriage with a deceased wife's sister, and by those who are in favour of that measure, each party striving to derive from the text an argument for the side which they are maintaining. But Holy Scripture ought not to be made a quarry whence partisans hew arguments for views which they have already adopted, nor is that the light in which a commentator can allow himself to regard it. A reverent and profound study of the passage before us, with its context, leads to the conclusion that the words have no bearing at all on the question of marriage with a deceased wife's sister, and thus it may be removed from the area and atmosphere of angry polemics. It is certain that the words translated a wife to her sister may be translated, in accordance with the marginal rendering, one wife to another. The objections made to such a version are arbitrary and unconvincing. It is in accordance with the genius of the Hebrew language to take "father," "son, brother," "sister," in a much wider acceptation than is the ease in the Western tongues. Anything that produces or causes is metaphorically a "father;" anything produced or caused is a "son;" any things akin to each other in form, shape, character, or nature, are "brothers" and "sisters." This is the name given to the loops of the curtains of the tabernacle (Exo_26:3, Exo_26:5, Exo_26:6), the tenons of the boards (Exo_26:17), and the wings of the cherubim (Eze_1:11, Eze_1:23). Indeed, wherever the expression, "a man to his brother," or "a woman to her sister," is used (and it is used very frequently) in the Hebrew Scriptures, it means not two brothers or two sisters, but two things or persons similar in kind. This does more than raise a presumption—it creates a high probability—that the expression should be understood in the same way here. But a difficulty then arises. If the right reading is, Neither shalt thou take one wife to another, does not the verse forbid polygamy altogether, and is not polygamy permitted by Exo_21:7-11; Deu_21:15-17; Deu_17:17? Certainly, if so important a restriction was to be made, we should expect it to be made directly, and in a manner which could not be disputed. Is there any way out of the difficulty? Let us examine each word of the Law. Neither shalt thou take one wife to another, to vex, to uncover her nakedness upon her in her life time. The two words, to vex, have not been sufficiently dwelt on. The Hebrew, tsarar, means to distress by packing closely together, and so, to vex, or to annoy in any way. Here is to be found the ground of the prohibition contained in the law before us. A man is not to take for a second wife a woman who is likely, from spiteful temper or for other reasons, to vex the first wife. Rachel vexed Leah; Peninnah vexed Hannah; the first pair were blood relations, the second were not; but under the present law the second marriage would in both cases have been equally forbidden, if the probability of the provocation had been foreseen. It follows that polygamy is not prohibited by the text before us, but that the liberty of the polygamist is somewhat circumscribed by the application of the law of charity. It follows, too, that the law has no bearing on the question of marriage with a deceased wife's sister, which is neither forbidden nor allowed by it. Are we then to conclude that the Law of Moses leaves the case of the wife's sister untouched? Not so, for the general principle has been laid down, None of you shall approach to any, that is near of kin to him, to uncover his nakedness, and, as we have seen, the expression, near of kin, includes relations by affinity equally with blood relations; as therefore the wife's sister is in the canonists' first degree of affinity (and in the second according to the civilians), it is reasonably inferred that marriage with her is forbidden under the above law, and this inference is confirmed by marriage with the other sister-in-law—the brother's wife—being, as the rule, prohibited. It can hardly be doubted that marriage with the grandmother and with the niece—both in the second degree of consanguinity according to the canonists, and the third degree according to the civilians—and incest with a daughter are forbidden under the same clause.

The present verse completes the Levitical code of prohibited degrees. The Roman code of restrictions on marriage was almost identical with the Mosaic tables. It only differed from them by specifically naming the grandmother and the niece among the blood relations with whom a marriage might not be contracted, and omitting the brother's wife among relatives by affinity. In the time of Claudius, a change was introduced into it, for the purpose of gratifying the emperor's passion for Agrippina, which legalized marriage with a brother's daughter. This legalization con-tinned in force until the time of Constantius, who made marriage with a niece a capital crime. The imperial code and the canon law were framed upon the Mosaic and the Roman tables, and under them no question arose, except as to the marriage of the niece, the decreased wife's sister, and the first cousin. Marriage with the niece was forbidden by Constantius, as we have said, in the year 355, on penalty of capital punishment for committing the offense, and marriage with a deceased wife's sister was declared by the same emperor to be null. The canons of Councils and the declarations of the chief Church teachers are in full accordance with the imperial legislation, condemning these marriages without a dissentient voice. The only ease in which no consensus is found is that of the marriage of first cousins. By the earliest Roman law these marriages had been disallowed (Tacitus, 'Annal.,' Deu_12:6), but in the second century B.C. they had become common (Livy, 42:34), and they continued to be lawful till the year A.D. 384 or 385, when Theodosius condemned them, and made them punishable by the severest penalties possible. This enactment lasted only twenty years, when it was repealed by Arcadius, A.D. 404 or 405. No adverse judgment respecting the marriage of first cousins was pronounced by the Church until after the legislation of Theodosius, but it appears that that legislation was promoted at her instance, and from that time forward the tendency to condemn these marriages became more and more pronounced. See the canons of the Councils of Agde, Epaone, Auvergne, Orleans, Tours, Auxerre, in the sixth century, and of the Council in Trullo in the seventh century. The reformers of the sixteenth century in England, entrenching themselves, as usual, behind the letter of Scripture and the practice of the primitive Church, forbade marriages of consanguinity and affinity in the first, second, and third degrees according to the reckoning of the civil law, and in the first and second degrees according to the reckoning of the canon law, excepting those of first cousins, on which the early Christians pronounced no decisive judgment.

The Pulpit Commentary
The marriage restrictions having been laid down, there follows in the five next verses the prohibition of five sexual impurities unconnected with marriage except by their subject-matter. The first is to approach unto a woman to uncover her nakedness, as long as she is put apart for her uncleanness, that is, either for seven days at the time of her ordinary illnesses (Lev_15:19), or any longer time that her illness might last (Lev_15:25), or for forty days after the birth of a man child (Lev_12:2-4), or for eighty days after the birth of a girl (Lev_12:5). The penalty for the offense within the seven days is death if committed willfully (Lev_20:18); if fallen into unknowingly, a ceremonial penalty of seven days' uncleanness is incurred (Lev_15:24). It is twice referred to by Ezekiel as a gross sin (Eze_18:6; Eze_22:10).

The Pulpit Commentary
The second prohibition is, Thou shalt not lie carnally with thy neighbour's wife—a prohibition already made in other words in the ten commandments. The punishment for adultery is death by stoning (Lev_20:10; Deu_22:22; Joh_9:5)—a more severe penalty than was usually inflicted in other nations.

The Pulpit Commentary
The third prohibition is, Thou shall not let any of thy seed pass through the fire to Molech. The words the fire are properly inserted, though not expressed in the original (cf. Deu_18:10; 2Ki_22:10). What was the nature and purpose of the idolatrous rite in question is, however, uncertain. It is generally assumed that reference is made to the practice of offering children in sacrifice to Molech, Deu_12:31, Eze_16:20, and Psa_106:37 being quoted in support of that view. But it is by no means certain that this was the case. It might have been a rite by which children were dedicated to Molech—a baptism by fire, not resulting in the death of the child. Its mention here, in close connection with carnal sins, has led some to regard it as an impure rite; but this is a mistaken inference, for the prohibition of adultery naturally suggests the prohibition of a spiritual unfaithfulness. That it was some kind of idolatrous ceremony is shown by the addition of the words, neither shalt thou profane the name of thy God. But if the children were burnt to death in honour of the idol, from the beginning, we should expect to find a notice of the fact in less ambiguous language than the expression, pass through the fire, conveys, earlier than the days of Ahaz. It is easy to imagine that what began as a dedication ceremony may have become converted into an absolute sacrifice, retaining still its original designation. Molech was a Canaanitish and Phoenician deity, the name meaning King, just as Baal means Lord (see Selden, 'De Diis Syris,' Psa_1:6). Jarchi, quoted by Wordsworth, describes the idol as "made of brass, having the face of an ox, with arms stretched out, in which the child was placed and burnt with fire, while the priests were beating drums, in order to drown the noise of its shrieks, lest the fathers might be moved with pity thereby." The place where the children were offered, in the later period of the Jewish history, was the valley of Hinnom (Jer_7:31; Jer_32:35; 2Ki_23:10).

The Pulpit Commentary
The fourth prohibition forbids the sin of Sodom (see Gen_19:5; Jdg_11:22; Rom_1:27; 1Co_6:9; 1Ti_1:10). The penalty is death (Lev_20:13).

The Pulpit Commentary
The fifth prohibition (see Herod; Lev_2:16). The penalty is death (Lev_20:15).