Thou shalt not lend upon usury to thy brother; usury of money, usury of victuals, usury of any thing that is lent upon usury: Unto a stranger thou mayest lend upon usury; but unto thy brother thou
shalt not lend upon usury: that the LORD thy God may bless thee in all
that thou settest thine hand to in the land whither thou goest to
possess it.
-- Deuteronomy 23:19f.