Yeremia 34:14

34:14 “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.” ¹  But your ancestors did not obey me or pay any attention to me.

[34:14]  ¹ sn Compare Deut 15:12-18 for the complete statement of this law. Here only the first part of it is cited.