1.

Why boastest thou thyself in mischief, O mighty man? the goodness of God endureth continually.

Title. Maschil= Instruction. The fifth of thirteen so named. See note on Title, Psalms 32 , and App-65 .
when Doeg, &c. See notes on 1 Samuel 21:7 ; 1 Samuel 22:18 . See note on Mahalath, in sub-scription at end of Psalms 52:9 .
Why boastest . . . ? Relating to Doeg's treachery.
mighty man. Hebrew. gibbor. App-14 . = tyrant; Septuagint = mighty lawless one. It is prophetic, and a type of Antichrist.
goodness = lovingkindness, or grace.
GOD . Hebrew El. App-4 .
continually = all the day.

2.

Thy tongue deviseth mischiefs; like a sharp rasor, working deceitfully.

mischiefs = malignity. Plural for singular = a great malignity.

3.

Thou lovest evil more than good; and lying rather than to speak righteousness. Selah.

evil. Hebrew. ra'a . App-44 .
Selah. Connecting the deceitful tongue of Doeg (Psalms 52:4 ) with the imprecation on it. See App-66 .

4.

Thou lovest all devouring words, O thou deceitful tongue.

devouring words. Hebrew words of swallowing up. Compare 1 Samuel 22:18 .

5.

God shall likewise destroy thee for ever, he shall take thee away, and pluck thee out of thy dwelling place, and root thee out of the land of the living. Selah.

destroy . . . take away. . . pluck out . . . root out. Note the Figure of speech Anabasis. App-6 .
Selah. Connecting God's judgment with the righteous onlookers. See App-66 .

6.

The righteous also shall see, and fear, and shall laugh at him:

righteous = righteous ones (plural)

7.

Lo, this is the man that made not God his strength; but trusted in the abundance of his riches, and strengthened himself in his wickedness.

the man = the strong man (Hebrew. geber. App-14 . IV) that made not God his strength. The Gematria of this sentence = 2,197 (= 133). See App-10 .
God. Hebrew. Elohim. App-4 .
trusted = confided. Hebrew. batah. App-69 .
wickedness. Aram, and Syriac read "wealth". Compare Psalms 112:3 .

8.

But I am like a green olive tree in the house of God: I trust in the mercy of God for ever and ever.

mercy = lovingkindness, or grace.

9.

I will praise thee for ever, because thou hast done it: and I will wait on thy name; for it is good before thy saints.

Thou hast done it. David ascribes all the glory to his God.
Thy name = Thyself. See note on Psalms 20:1 .
Thy saints. Some codices read singular = Thy beloved (One).