Let see how the other part of God’s laws, they can get a male Hebrew slave to become a permanent slave by keeping his wife and children hostage until he says he wants to become a permanent slave.
Exodus 21:2-6
If he was single when he became your slave and then married afterward, only he will go free in the seventh year. But if he was married before he became a slave, then his wife will be freed with him. If his master gave him a wife while he was a slave, and they had sons or daughters, then the man will be free in the seventh year, but his wife and children will still belong to his master. But the slave may plainly declare, 'I love my master, my wife, and my children. I would rather not go free.' If he does this, his master must present him before God. Then his master must take him to the door and publicly pierce his ear with an awl. After that, the slave will belong to his master forever.
After going one big round, you are still able to keep your slave indefinitely. How crafty is this law? This is very similar to the modern laws used by facist governments and some financial instruments(mini bonds) to exploit the peasants.
This is one of the many examples of the ‘Good’ biblical family values!