For it is written that Avraham had two sons, one by the handmaid, and one by the free woman.
Hagar bore a son for Avram. Avram called the name of his son, whom Hagar bore, Yishma'el.
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.*
However, the son by the handmaid was born according to the flesh, but the son by the free woman was born through promise.
However what does the Scripture say? *Throw out the handmaid and her son, for the son of the handmaid will not inherit with the son of the free woman.*
So then, brothers, we are not children of a handmaid, but of the free woman.