Genesis 47:22
Only the land of the priests bought he not; for the priests had a portion assigned them of Pharaoh, and did eat their portion which Pharaoh gave them: wherefore they sold not their lands. Only the land of the priests bought he not; for the priests had a portion assigned them of Pharaoh, and did eat their portion which Pharaoh gave them: wherefore they sold not their lands.
This text belongs to the account of Joseph managing the famine in Egypt. The priests kept their lands because Pharaoh gave them an assigned portion of food to live on, so they did not need to sell. Like the priests, Jacob's family did not sell their land or themselves for food as many Egyptians did.
Pharaoh granted Jacob's family land in Goshen, Joseph supplied them with food liberally, and they paid no tax. This place and provision in Egypt was granted in gratitude for Joseph's service and wise management.