Galatians 4:22
for it hath been written, that Abraham had two sons, one by the maid-servant, and one by the free-woman,
Genesis 16:15
And Hagar beareth to Abram a son; and Abram calleth the name of his son, whom Hagar hath borne, Ishmael;
Genesis 16:2-4
and Sarai saith unto Abram, 'Lo, I pray thee, Jehovah hath restrained me from bearing, go in, I pray thee, unto my handmaid; perhaps I am built up from her;' and Abram hearkeneth to the voice of Sarai.
Genesis 21:1-2
And Jehovah hath looked after Sarah as He hath said, and Jehovah doth to Sarah as He hath spoken;
Genesis 21:10
and she saith to Abraham, 'Cast out this handmaid and her son; for the son of this handmaid hath no possession with my son -- with Isaac.'