Matthew Poole and continuators on Genesis 17:4

4. As for me, behold my covenant is with thee; and thou shalt be a father of many nations .

Both literally, or after the Flesh, of the Israelites, Ismaelites, Edomites, &c. and spiritually, of all Believers of all Nations, to whom Abram hath in some sort the place of a Father, Rom. 4. 12, 17. Not only as he was the great example and teacher of that faith by which they are all saved (as the instructers of others are called their Fathers, both in Scripture, as Gen. 4. 20, 21. and in profane Authors) but as he was made by God the head of the Covenant, by, or through whom the Covenant-right was conveyed to all his natural seed, and afterwards to the spiritual seed, all Gentile-Believers.

Marginal references: Heb. multitude of Nations.