Leviticus 25:43

40 But as an hired servant, and as a sojourner, he shall be with thee, and shall serve thee unto the year of jubile:

41 And then shall he depart from thee, both he and his children with him, and shall return unto his own family, and unto the possession of his fathers shall he return.

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

43 Thou shalt not rule over him with rigour; but shalt fear thy God.

44 Both thy bondmen, and thy bondmaids, which thou shalt have, shall be of the heathen that are round about you; of them shall ye buy bondmen and bondmaids.

45 Moreover of the children of the strangers that do sojourn among you, of them shall ye buy, and of their families that are with you, which they begat in your land: and they shall be your possession.

46 And ye shall take them as an inheritance for your children after you, to inherit them for a possession; they shall be your bondmen for ever: but over your brethren the children of Israel, ye shall not rule one over another with rigour.