John Gill Commentary Proverbs 21:2

"Every way of a man is right in his own eyes; But Jehovah weigheth the hearts." — Proverbs 21:2 (ASV)

Every way of a man [is] right in his own eyes
This is repeated, from (Proverbs 16:2Proverbs 16:25); 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.