A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
psa 73:1Of Asaph--(see Introduction). God is good to His people. For although the prosperity of the wicked, and the afflictions of the righteous, tempted the Psalmist to misgivings of God's government, yet the sudden and fearful ruin of the ungodly, seen in the light of God's revelation, reassures his heart; and, chiding himself for his folly, he is led to confide renewedly in God, and celebrate His goodness and love. (Psa. 73:1-28)
The abrupt announcement of the theme indicates that it is the conclusion of a perplexing mental conflict, which is then detailed (compare Jer 12:1-4).
Truly--or, "Surely it is so."
clean heart-- (Psa 18:26) describes the true Israel.
psa 73:2The figures express his wavering faith, by terms denoting tottering and weakness (compare Psa 22:5; Psa 62:3).
psa 73:3The prosperous wicked are insolently proud (compare Psa 5:5). They die, as well as live, free from perplexities: pride adorns them, and violence is their clothing; indeed they are inflated with unexpected success. With all this--
psa 73:8They are corrupt--or, literally, "they deride," they speak maliciously and arrogantly and invade even heaven with blasphemy (Rev 13:6), and cover earth with slanders (Job 21:7-14).
psa 73:10Hence God's people are confounded, turned hither (or back) and thither, perplexed with doubts of God's knowledge and care, and filled with sorrow.
psa 73:12prosper in the word--literally, "secure for ever."
psa 73:13The Psalmist, partaking of these troubles, is especially disturbed in view of his own case, that with all his diligent efforts for a holy life, he is still sorely tried.
psa 73:15Freed from idiomatic phrases, this verse expresses a supposition, as, "Had I thus spoken, I should," &c., intimating that he had kept his troubles to himself.
generation of thy children--Thy people (Jo1 3:1).
offend--literally, "deceive, mislead."
psa 73:16Still he--
thought--literally, "studied," or, "pondered this riddle"; but in vain; it remained a toil (compare Margin), till he--
psa 73:17went into the sanctuary--to enquire (compare Exo 25:22; Psa 5:7; Psa 27:4).
psa 73:18their end--future (Psa 37:37-38), which is dismal and terribly sudden (Pro 1:27; Pro 29:1), aggravated and hastened by terror. As one despises an unsubstantial dream, so God, waking up to judgment (Psa 7:6; Psa 44:23), despises their vain shadow of happiness (Psa 39:6; Isa 29:7). They are thrown into ruins as a building falling to pieces (Psa 74:3).
psa 73:21He confesses how--
foolish--literally, "stupid," and
ignorant--literally, "not discerning," had been his course of thought.
psa 73:22before thee--literally, "with Thee," in conduct respecting Thee.
psa 73:23Still he was with God, as a dependent beneficiary, and so kept from falling (Psa 73:2).
psa 73:24All doubts are silenced in confidence of divine guidance and future glory.
receive me to glory--literally, "take for (me) glory" (compare Psa 68:18; Eph 4:8).
psa 73:25God is his only satisfying good.
psa 73:26strength--literally, "rock" (Psa 18:2).
portion-- (Psa 16:5; Lam 3:24).
psa 73:27The lot of apostates, described by a figure of frequent use (Jer 3:1, Jer 3:3; Eze 23:35), is contrasted with his, who finds happiness in nearness to God (Jam 4:8), and his delightful work the declaration of His praise.