Charles H. Spurgeon on Psalms 37:21

The wicked borroweth, and payeth not again. Partly because he will not, but mainly because he cannot. Want follows upon waste, and debt remains undischarged. Often are the wicked thus impoverished in this life. Their wanton extravagance brings them down to the usurer's door and to the bankrupt's suit. But the righteous sheweth mercy, and giveth, Mercy has given to him, and therefore he gives in mercy. He is generous and prosperous. He is not a borrower, but a giver. So far as the good man can do it, he lends an ear to the requests of need, and instead of being impoverished by what he imparts, he grows richer, and is able to do more. He does not give to encourage idleness, but in real mercy, which supposes real need. The text suggests to us how much better it generally is to give than to lend. Generally, lending comes to giving in the end, and it is as well to anticipate the fact, and by a little liberality forestall the inevitable. If these two sentences describe the wicked and the righteous, the writer of these lines has reason to know that in and about the city of London the wicked are very numerous.