Galatians 4:22
For it is written that Abraham had two sons, one by a slave woman and one by a free woman.
Genesis 16:15
And Hagar bore Abram a son, and Abram called the name of his son, whom Hagar bore, Ishmael.
Genesis 16:2-4
And Sarai said to Abram, "Behold now, the LORD has prevented me from bearing children. Go in to my servant; it may be that I shall obtain children by her." And Abram listened to the voice of Sarai.
Genesis 21:1-2
The LORDvisited Sarah as he had said, and the LORD did to Sarah as he had promised.
Genesis 21:10
So she said to Abraham, "Cast out this slave woman with her son, for the son of this slave woman shall not be heir with my son Isaac."