Deuteronomy 23:19
Thou shalt not lend upon usury to thy brother; usury of money, usury of victuals, usury of any thing that is lent upon usury: Thou shalt not lend upon usury to thy brother; usury of money, usury of victuals, usury of any thing that is lent upon usury:
The command forbids charging interest or any increase to a fellow Israelite brother on anything lent, whether money, food, victuals, or anything else that is lent upon usury. A stranger or foreigner may be charged interest, but a brother Israelite, understood as a fellow believer, may not. The distinction is between a brother who is to be helped without interest and a stranger to whom interest may be charged.
The prohibition especially protects a borrower in need, above all a poor brother in hardship and distress, from being exploited when he borrows. The wealthy must not profit from his distress to enrich themselves and increase their own wealth. Instead lending is to be governed by mercy and regard for the borrower's rights, with practical help given rather than advantage taken.
Obedience to this command is connected with God's blessing, including blessing in the land. That principle condemns oppressive lending that enriches the lender from a poor neighbor's need. Charging ten or twelve percent interest is unjust before God even where human law permits it.