וַתָּשֻׁ֙בוּ֙ וַתְּחַלְּל֣וּ אֶת־שְׁמִ֔י וַתָּשִׁ֗בוּ אִ֤ישׁ אֶת־עַבְדּוֹ֙ וְאִ֣ישׁ אֶת־שִׁפְחָת֔וֹ אֲשֶׁר־שִׁלַּחְתֶּ֥ם חָפְשִׁ֖ים לְנַפְשָׁ֑ם וַתִּכְבְּשׁ֣וּ אֹתָ֔ם לִֽהְי֣וֹת לָכֶ֔ם לַעֲבָדִ֖ים וְלִשְׁפָחֽוֹת׃ (ס)
but ye turned and profaned My name, and caused every man his servant, and every man his handmaid, whom ye had let go free at their pleasure, to return; and ye brought them into subjection, to be unto you for servants and for handmaids.
Read Jewish philosophy on Jeremiah 34:16: Rambam's Guide for the Perplexed, Saadia Gaon, and classical Jewish philosophical sources, free online.