Exodus 21:2-6

“When you buy a Hebrew slave, he will serve six years. The seventh year he goes free, for nothing. If he came in single he leaves single. If he came in married he leaves with his wife. If the master gives him a wife and she gave him sons and daughters, the wife and children stay with the master and he leaves by himself. But suppose the slave should say, ‘I love my master and my wife and children—I don’t want my freedom,’ then his master is to bring him before God and to a door or doorpost and pierce his ear with an awl, a sign that he is a slave for life.