Galatians 4:22
For it is written, that Abraham had two sons, one by the handmaid, and one by the freewoman.
Genesis 16:15
And Hagar bare Abram a son: and Abram called the name of his son, whom Hagar bare, Ishmael.
Genesis 16:2-4
And Sarai said unto Abram, Behold now, Jehovah hath restrained me from bearing; go in, I pray thee, unto my handmaid; it may be that I shall obtain children by her. And Abram hearkened to the voice of Sarai.
Genesis 21:1-2
And Jehovah visited Sarah as he had said, and Jehovah did unto Sarah as he had spoken.
Genesis 21:10
Wherefore she said unto Abraham, Cast out this handmaid and her son. For the son of this handmaid shall not be heir with my son, even with Isaac.