Exodus 21:2
2 gWhen you buy a Hebrew slave,1 he shall serve six years, and in the seventh he shall go out free, for nothing.
Jeremiah 34:14
14 c‘At the end of seven years each of you must set free the fellow Hebrew who has been sold to you and has served you six years; you must set him free from your service.’ But your fathers did not dlisten to me or incline their ears to me.
Leviticus 25:39–41
39 “If your brother becomes poor beside you rand sells himself to you, you shall not make him serve as a sslave: 40 he shall be with you as a hired worker and as a sojourner. He shall serve with you until the year of the jubilee. 41 Then he shall go out from you, he and his children with him, and go back to his own clan and return to the possession of his fathers.