What does Jeremiah 34:8 mean?

You will die in peace; and with the burnings of your fathers, the former kings who were before you, so they will make a burning for you. They will lament you, saying, “Ah Lord!” for I have spoken the word,’ says Yahweh.”

Then Jeremiah the prophet spoke all these words to Zedekiah king of Judah in Jerusalem,

when the king of Babylon’s army was fighting against Jerusalem, and against all the cities of Judah that were left, against Lachish and against Azekah; for these alone remained of the cities of Judah as fortified cities.

that every man should let his male servant, and every man his female servant, who is a Hebrew or a Hebrewess, go free; that no one should make bondservants of them, of a Jew his brother.

All the princes and all the people obeyed who had entered into the covenant, that everyone should let his male servant, and everyone his female servant go free, that no one should make bondservants of them any more. They obeyed and let them go;

but afterwards they turned, and caused the servants and the handmaids, whom they had let go free, to return, and brought them into subjection for servants and for handmaids.