It would be through Isaac that Abraham's seed would be named.
Genesis 21:12 And God said unto Abraham, Let it not be grievous in thy sight because of the lad, and because of thy bondwoman; in all that Sarah hath said unto thee, hearken unto her voice; for in Isaac shall thy seed be called.
Ishmael is called the seed of Hagar but never called the seed of Abraham. It was 13 years after the birth of Ishmael that God changed Abram to Abraham and promised:
Genesis 17:7 "And I will establish my covenant between me and you and your seed after you throughout their generations for an everlasting covenant, to be God to you and to your seed after you. 8 And I will give to you and to your seed after you the land of your sojournings, all the land of Canaan, for an everlasting possession, and I will be their God.
Notice that God never said He would be the God of the seed of Hagar. When Abraham said he wanted Ishmael to live before God he was told no that it was going to Isaac.
Genesis 17:18 And Abraham said unto God, O that Ishmael might live before thee! 19 And God said, Sarah thy wife shall bear thee a son indeed; and thou shalt call his name Isaac: and I will establish my covenant with him for an everlasting covenant, and with his seed after him.
God never said He would be a God to Ishmael. He said He would be a God to Isaac.
I serve the God of Abraham, Isaac, and Jacob. I do not serve the same god as the Muslims.
“God never said He would be a God to Ishmael.”
He did to Abraham. Muslims say they worship the God of Abraham.
“He said He would be a God to Isaac.”
And Abraham before him. Muslims say they worship the God of Abraham.
“serve the God of Abraham, Isaac, and Jacob. I do not serve the same god as the Muslims.”
So the God of Abraham is not the God of Abraham - that’s what you’re saying.