Galatians 4:22
For it is written that Abraham had two sons, one from the servant girl, and one from the freewoman.
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, LORD has restrained me from bearing. Go in, I pray thee, to my handmaid. It may be that I will obtain sons by her. And Abram hearkened to the voice of Sarai.
Genesis 21:1-2
And LORD visited Sarah as he had said, and LORD 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 shall not be heir with my son, even with Isaac.