Genesis 21:13
"And also of the son of the bondwoman will I make a nation, because he is thy seed."
Cross References (ranked by relevance)
Genesis 16:10
And the angel of the LORD said unto her, I will multiply thy seed exceedingly, that it shall not be numbered for multitude.
Genesis 17:20
And as for Ishmael, I have heard thee: Behold, I have blessed him, and will make him fruitful, and will multiply him exceedingly; twelve princes shall he beget, and I will make him a great nation.
Genesis 21:18
Arise, lift up the lad, and hold him in thine hand; for I will make him a great nation.