Albert Barnes Commentary Psalms 37:21

"The wicked borroweth, and payeth not again; But the righteous dealeth graciously, and giveth." — Psalms 37:21 (ASV)

The wicked borroweth, and payeth not again - This is probably intended here, not so much to describe the character as the condition of the wicked. The idea is that he will be in such a condition of want that he will be under a necessity of borrowing but will not have the means of repaying what he has borrowed, while the righteous will not only have enough for himself but will also have the means of showing mercy to others and of giving to them what they need. The ability to lend to others is referred to as a part of the promise of God to his people, and as marking their condition as a prosperous one, in Deuteronomy 15:6: And thou shalt lend unto many nations, and thou shalt not borrow. Compare Deuteronomy 28:12 and Deuteronomy 28:44.

It is true, however, that a wicked man is characteristically often disposed to borrow and not pay again; he will be reckless about borrowing and careless about paying. In contrast, it is characteristic of a good or upright man that he will not borrow when he can avoid it, and that he will be punctual and conscientious in paying what he has borrowed.

But the righteous showeth mercy, and giveth - That is, in this connection, he is not under the necessity of borrowing from others for the supply of his wants. He not only has enough for himself, but he also has the means of aiding others and has the disposition to do it. It is his character to show favors, and he has the means of gratifying this desire.

And giveth - He imparts to others. He has enough for himself and also has that which he can give to others. Of course, all this is designed to be general. It does not mean that this will universally be the case, but that the tendency of a life of piety is to make a man prosperous in his worldly affairs, to give him what he needs for himself, and to furnish him with the means, as he has the disposition, to do good to others. Other things being equal, the honest, temperate, pure, pious man will be the most prosperous in the world: for honesty, temperance, purity, and piety produce the industry, economy, and prudence on which prosperity depends.