"If your kinsman, being in straits, comes under your authority, and you hold him as though a resident alien, do not exact from him advance or accruted interest, but fear your God. Let him live by your side as a kinsman. Do not lend him money at advance interest, or give him your food at accrued interest. I the Lord am your God, who brought you out of the land of Egypt, to give you the land of Canaan, to be your God.

If your kinsman under you continues in straits and must give himself over to you, do not subject him to the treatment of a slave. He shall remain with you as a hired or bound laborer; he shall serve with you only until the Jubilee year."
Leviticus 25:35-40

The interesting thing here, obviously, is the way that interest is regarded as something to be avoided.