Deuteronomy 23:19 - Joseph Benson’s Commentary on the Old and New Testaments

Thou shalt not lend upon usury to thy brother To an Israelite. They held their estates immediately from God, who, while he distinguished them from all other people, might have ordered, had he pleased, that they should have all things in common. But instead of that, and in token of their joint interest in the good land he had given them, he only appointed them, as there was occasion, to lend to one another without interest. This, among them, would be little or no loss to the lender, because their land was so divided, their estates so settled, and there was so little merchandise among them, that it was seldom or never they had occasion to borrow any great sums, but only for the subsistence of their families, or some uncommon emergence. But they might lend to a stranger upon usury who was supposed to live by trade, and therefore got by what he borrowed: in which case it is just the lender should share in the gain. This usury, therefore, is not oppressive; for they might not oppress a stranger.