Jeremiah 34:13-14

13“Thus says the Lord, the God of Israel, ‘I made a covenant (solemn pledge) with your forefathers in the day that I brought them out of the land of Egypt, out of the house of bondage, saying,

14“At the end of seven years each of you shall set free his Hebrew brother who has sold himself [into servitude] or who has been sold to you and has served you six years, you shall release him from [serving] you; but your forefathers did not listen [submissively] to Me or obey Me.