Deuteronomy 15:12
If your fellow Hebrew -- whether male or female -- is sold to you and serves you for six years, then in the seventh year you must let that servant go free.
Jeremiah 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." But your ancestors did not obey me or pay any attention to me.
Leviticus 25:39-41
"'If your brother becomes impoverished with regard to you so that he sells himself to you, you must not subject him to slave service.
Exodus 21:2-6
"If you buy a Hebrew servant, he is to serve you for six years, but in the seventh year he will go out free without paying anything.
Deuteronomy 15:1
At the end of every seven years you must declare a cancellation of debts.
John 8:35-36
The slave does not remain in the family forever, but the son remains forever.