The Pulpit Commentary
Why boastest thou thyself in mischief, O mighty man? Doeg was "the chiefest of the herdmen that belonged to Saul" (1Sa_21:7), or, according to another passage (1Sa_22:9), "set over the servants of Saul." The position would be a high one, and would imply the possession of much physical strength. A sense of tyranny or extreme arrogance seems to attach to the word translated "mighty one" (gibber); see Gen_6:4; Gen_10:8. The word translated "mischief" implies something worse. In Psa_6:9 it is rendered "wickedness," and is thought to mean, in the Psalms generally, "ruinous, unfathomable evil—destructive malignity" (Canon Cook). The goodness of God endureth continually. Why not follow the Divine pattern, instead of setting thyself in direct antagonism to it? Canst thou expect to prosper when thou art thus opposed to the Almighty?

The Pulpit Commentary
Thy tongue deviseth mischiefs; or, malignities—evils of the worst kind. It was Doeg's "tongue" that brought about the entire ghastly massacre (see 1Sa_22:9, 1Sa_22:10). Like a sharp razor, working deceitfully. Doeg had "worked deceitfully," since he had not told Saul the circumstances that made Ahimelech's giving aid to David no disloyalty to the king (1Sa_21:2, 1Sa_21:8). The suppressio veri is a suggestio falsi.

The Pulpit Commentary
Thou lovest evil more than good. To "love evil" is to have reached the lowest depth of depravity. It is to say, with Milton's Satan, "Evil, be thou my good!" And lying rather than to speak righteousness (see the comment on Psa_52:2). Doeg's crimes seem to have arisen out of a mere love of evil.

The Pulpit Commentary
Thou lovest all devouring words. "Devouring words" are words that cause ruin and destruction. O thou deceitful tongue! or, and the deceitful tongue.

The Pulpit Commentary
God shall likewise destroy thee for ever. As thy "devouring words" have been the destruction of many, so shall God, in return, "destroy thee" (literally, pull thee down) "for ever"—destroy thee, i.e; with a complete and final destruction. He shall take thee away; rather, seize thee (Kay, Cheyne), and pluck thee out of thy dwelling-place; literally, out of thy tent (comp. Job_18:14; 1Ki_12:16). And root thee out of the land of the living. Destroy thee, root and branch, as thou didst destroy the entire house of Ahimelech (1Sa_22:17-19).

The Pulpit Commentary
The righteous also shall see, and fear. Every manifestation of the Divine power and justice produces in the righteous man a feeling of awe. And shall laugh at him; literally, over him. This awe does not, however, prevent him from indulging in something like derision of his fallen enemy—or, at least, it did not under the old covenant, when men had not yet been taught that they ought to "love" their enemies.

The Pulpit Commentary
Lo, this is the man that made not God his strength. The root of Doeg's wickedness was want of trust in God, and consequent alienation from him. But trusted in the abundance of his riches. This led on to an excessive trust in riches, and greediness of gain. To obtain wealth he became Saul's unscrupulous tool, the willing instrument of his cruelty. No doubt Saul richly rewarded him. And strengthened himself in his wickedness; or, in his substance (Cheyne).

The Pulpit Commentary
But I am like a green olive tree in the house of God. In conclusion, the psalmist contrasts his own condition, as one of God's people, with that of Doeg, which he had described in Psa_52:7-9. Doeg is about to be "plucked up" and "rooted out of the land of the living" (Psa_52:5); he is like a flourishing green olive tree planted in the sanctuary, or "house of God." Doeg is entirely without any trust in the Almighty (Psa_52:7); he declares of himself, I trust in the mercy of God for ever and ever. It is questioned whether olive trees were at any time planted in the courts of either the tabernacle or the temple; but it certainly cannot be proved that they were not. In the courts of Egyptian temples trees were abundant, also probably in Phoenician temples. And to this day there grow in the Hardin area at Jerusalem, on the site of the Jewish temple, a number of magnificent cypresses, olive, and lemon trees.

The Pulpit Commentary
I will praise thee for ever, because thou hast done it. So Dr. Kay, who explains the passage as meaning, "because thou hast worked out this deliverance.' The tense is "the preterite of prophetic certainty" (comp. Psa_54:7). And I will wait on thy Name; for it is good before thy saints; rather, I will wait on thy Name in the presence of thy saints, because it is good; or perhaps, if we adopt Hupfeld's emendation (אֲחַוֶּה for אֲקַוֶּה), I will precision thy Name before thy saints that it is good (so Cheyne).