Genesis 47:23-26

23Joseph said to the people, ‘Now I have bought you and your land for Pharaoh. So I will give you some seed to plant in your fields.

24But when the plants are ready to eat, you must give one fifth part to Pharaoh. You may keep the other four parts. You may keep it for seed to plant again and you may eat it. It will be food for you, for your people and for your children.’

25The people said, ‘You have saved our lives! Because you have been kind to us, we agree to become Pharaoh's slaves.’

26So Joseph made a law which everybody in Egypt has to obey. The law says that one fifth of all food that people grow belongs to Pharaoh. Only the priests' land did not become Pharaoh's land. This law still has authority today.