John Gill Commentary Psalms 37:21

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

The wicked borrows, and pays not again
While the wicked live, they are scandalous; they live by borrowing, which was always reckoned mean; see (Deuteronomy 28:12Deuteronomy 28:44) (Proverbs 22:7) ; and what is worse, as they borrow, they do not design to repay; they take no care nor thought about that, but live upon what they borrow: for this either expresses their incapacity that they cannot pay; or the evil disposition of their mind, which rather seems to be the sense, that they will not pay;

but the righteous shows mercy, and gives ;
which not only argues capacity and ability, but a kind, merciful, and tender spirit to persons in distress, and is expressive of a generous action.