Exodus 21:5-6

5But perhaps the slave may say, “I love my master, my wife and my children. I will not go away as a free man!”

6Then his master must take the slave to stand in front of the judges. He must lead the slave to stand beside the door, or the wood that holds the door. Then the master must push the sharp point of a tool through the slave's ear. After that, he will serve his master for all his life.