| Clarke's Commentary on the Bible The Lord pondereth the hearts - Every man feels strongly attached to his own opinions, modes of acting, etc.; and though he will not easily give up any thing to the judgment of a neighbor, whom he will naturally consider at least as fallible as himself, yet he should consider that the unerring eye of God is upon him; and he should endeavor to see that what he does is acceptable in the eye of his Maker and Judge.
Gill's Exposition of the Entire BibleEvery way of a man is right in his own eyes,.... This is repeated, from Proverbs 16:2; for the confirmation of it; and that it might be observed and taken notice of, and men be brought under a conviction of it; which is not easily done, it being what affects all men: every man is conceited of himself and his own way, and is not easily persuaded off of it; his sinful ways are agreeable to him promising him pleasure, profit, or honour; and his self-righteous ways suit with the vain opinion he has of himself, whereby he promises himself eternal life and happiness. The Septuagint and Arabic versions render it to this sense, "every man seems righteous to himself;'' but the Lord pondereth the hearts: weighs them in the balance of righteousness and truth; considers them, having a perfect knowledge of them, and all the springs of action in them; and knows that every way of man is not right, though they may seem so to him.
Keil and Delitzsch Biblical Commentary on the Old TestamentThe next group extends from Proverbs 21:2 to Proverbs 21:8, where it closes as it began. 2 Every way of a man is right in his own eyes; But a weigher of hearts is Jahve. A proverb similar to Proverbs 16:2 (where דּרכי, for דּרך, זך for ישׁר, רוּחות for לבּות). God is also, Proverbs 17:3, called a trier, בּחן, of hearts, as He is here called a weigher, תּכן. The proverb indirectly admonishes us of the duty of constant self-examination, according to the objective norm of the revealed will of God, and warns us against the self-complacency of the fool, of whom Proverbs 12:15 says (as Trimberg in "Renner"): "all fools live in the pleasant feeling that their life is the best," and against the self-deception which walks in the way of death and dreams of walking in the way of life, Proverbs 14:12 (Proverbs 16:25).
Geneva Study BibleEvery way of a man is right in his own eyes: but the LORD pondereth the hearts.
Jamieson-Fausset-Brown Bible Commentary2. (Compare Pr 14:2; 16:2-25).
Matthew Henry's Concise Commentary21:1 The believer, perceiving that the Lord rules every heart as he sees fit, like the husbandman who turns the water through his grounds as he pleases, seeks to have his own heart, and the hearts of others, directed in his faith, fear, and love. 2. We are partial in judging ourselves and our actions. 3. Many deceive themselves with a conceit that outward devotions will excuse unrighteousness. 4. Sin is the pride, the ambition, the glory, the joy, and the business of wicked men. 5. The really diligent employ foresight as well as labour. 6. While men seek wealth by unlawful practices, they seek death. 7. Injustice will return upon the sinner, and will destroy him here and for ever. 8. The way of mankind by nature is froward and strange.
Matthew Henry's Whole Bible CommentaryVerse 2 Note, 1. We are all apt to be partial in judging of ourselves and our own actions, and to think too favourably of our own character, as if there was nothing amiss in it: Every way of a man, even his by-way, is right in his own eyes. The proud heart is very ingenious in putting a fair face upon a foul matter, and in making that appear right to itself which is far from being so, to stop the mouth of conscience. 2. We are sure that the judgment of God concerning us is according to truth. Whatever our judgment is concerning ourselves, the Lord ponders the heart. God looks at the heart, and judges of men according to that, of their actions according to their principles and intentions; and his judgment of that is as exact as ours is of that which we ponder most, and more so; he weighs it in an unerring balance, ch. 16:2. | 
