Jer 34:14

מִקֵּ֣ץ שֶׁ֣בַע שָׁנִ֡ים תְּֽשַׁלְּח֡וּ אִישׁ֩ אֶת־אָחִ֨יו הָעִבְרִ֜י אֲשֶֽׁר־יִמָּכֵ֣ר לְךָ֗ וַעֲבָֽדְךָ֙ שֵׁ֣שׁ שָׁנִ֔ים וְשִׁלַּחְתּ֥וֹ חָפְשִׁ֖י מֵֽעִמָּ֑ךְ וְלֹֽא־שָׁמְע֤וּ אֲבֽוֹתֵיכֶם֙ אֵלַ֔י וְלֹ֥א הִטּ֖וּ אֶת־אָזְנָֽם׃

Every seventh year, each of you must free his Hebrew brother who has sold himself to you. He may serve you six years, but then you must let him go free. But your fathers did not listen or incline their ear.