Jeremiah 34:13-14

13“The Lord God of Israel has a message for you. ‘I made a covenant with your ancestors when I brought them out of Egypt where they had been slaves. It stipulated,

14“Every seven years each of you must free any fellow Hebrews who have sold themselves to you. After they have served you for six years, you shall set them free.” But your ancestors did not obey me or pay any attention to me.