Leviticus 25:45

42 For they are my servants, whom I brought forth out of the land of Egypt: they shall not be sold as bondservants.

43 You shall not rule over him with rigor, but shall fear your God.

44 As for your bondservants, and your bondmaids, whom you shall have; of the nations that are round about you, of them shall you buy bondservants and bondmaids.

45 Moreover of the children of the strangers who sojourn among you, of them shall you buy, and of their families who are with you, which they have conceived in your land: and they shall be your possession.

46 You shall make them an inheritance for your children after you, to hold for a possession; of them shall you take your bondservants forever: but over your brothers the children of Israel you shall not rule, one over another, with rigor.

47 If a stranger or sojourner with you has grown rich, and your brother has grown poor beside him, and sell himself to the stranger [or] sojourner with you, or to the stock of the stranger`s family;

48 after that he is sold he may be redeemed: one of his brothers may redeem him;