Galatians 4:22
For it is written that Abraham had two sons, one by the handmaid, and one by the free woman.
Genesis 16:15
Hagar bore a son for Abram. Abram called the name of his son, whom Hagar bore, Ishmael.
Genesis 16:2-4
Sarai said to Abram, "See now, Yahweh has restrained me from bearing. Please go in to my handmaid. It may be that I will obtain children by her." Abram listened to the voice of Sarai.
Genesis 21:1-2
Yahweh visited Sarah as he had said, and Yahweh did to Sarah as he had spoken.
Genesis 21:10
Therefore she said to Abraham, "Cast out this handmaid and her son! For the son of this handmaid will not be heir with my son, Isaac."