Psalms 37:21

These verses are much to the same purport with the foregoing verses of this psalm, for it is a subject worthy to be dwelt upon. Observe here, I. What is required of us as the way to our happiness, which we may learn both from the characters here laid down and from the directions here given. If we would be blessed of God, 1. We must make conscience of giving every body his own; for the wicked borrows and pays not again, Psa 37:21. It is the first thing which the Lord our God requires of us, that we do justly, and render to all their due. It is not only a shameful paltry thing, but a sinful wicked thing, not to repay what we have borrowed. Some make this an instance, not so much of the wickedness of the wicked as of the misery and poverty to which they are reduced by the just judgment of God, that they shall be necessitated to borrow for their supply and then be in no capacity to repay it again, and so lie at the mercy of their creditors. Whatever some men seem to think of it, as it is a great sin for those that are able to deny the payment of their just debts, so it is a great misery not to be able to pay them. 2.

— Matthew Henry's Concise Commentary (public domain)

payeth not--not able; having grown poor (compare Deu 15:7). Ability of the one and inability of the other do not exclude moral dispositions. God's blessing or cursing makes the difference.

— Jamieson-Fausset-Brown Commentary (public domain)