Leviticus 25:43

And Joseph said to them on the third day, “Do this and live, for I fear God:

“If you buy a Hebrew slave, he shall serve for six years; but on the seventh he shall go out as a free man without payment.

‘You may even give them as an inheritance to your sons after you, to receive as a possession; you can use them as permanent slaves. But in respect to your brothers, the sons of Israel, you shall not have dominion over one another with brutality.

‘Like a man hired year by year he shall be with him; he shall not have dominion over him with brutality in your sight.

“If your brother, a Hebrew man or woman, is sold to you, then he shall serve you six years, but in the seventh year you shall let him go to be free from you.

“You shall not oppress a hired person who is afflicted and needy, whether he is one of your brothers or one of your sojourners who is in your land within your gates.

The word which came to Jeremiah from Yahweh after King Zedekiah had cut a covenant with all the people who were in Jerusalem to proclaim release to them:

And masters, do the same things to them, giving up threatening, knowing that both their Master and yours is in heaven, and there is no partiality with Him.