A bondservant doesn't live in the house forever. A son remains forever.
Therefore she said to Avraham, *Cast out this handmaid and her son! For the son of this handmaid will not be heir with my son, Yitzchak.*
But if he give of his inheritance a gift to one of his servants, it shall be his to the year of liberty; then it shall return to the prince; but as for his inheritance, it shall be for his sons.
*He said to him, 'Son, you are always with me, and all that is mine is yours.
For you died, and your life is hidden with Messiah in God.
But he, because he lives forever, has his priesthood unchangeable.