184.

Did God say that the promise of blessing upon Abraham’s descendants would specifically come through the lineage of Isaac and not Ishmael?

Bible: Yes Qur'an: No

Genesis 16:11-12 – 11. And the angel of the LORD said unto her, Behold, thou art with child, and shalt bear a son, and shalt call his name Ishmael... 12. And he will be a wild man; his hand will be against every man, and every man's hand against him.

Genesis 17:18-21 – 21. my covenant will I establish with Isaac, which Sarah shall bear unto thee at this set time in the next year.

An-Nisa 4:163 – We sent revelation upon Abraham and upon Ishmael... and Jesus...

Maryam 19:54 – Ishmael... he was a messenger (of Allah), a Prophet.