LOL, this is funny man. I know that he will establish a covenant with Isaac. My objection is to the fact that when GOD said your only son, it can't be Isaac. Let me put it this way.
Ishmael was born before Isaac, then Isaac is born, then GOD said to Abraham take YOUR ONLY SON ISAAC and kill him. How can Isaac be his only son when Ishamel is already around and older than Isaac?
Also, what is a "great nation" means do you think?
Another question, OVERLASTING COVENANT means an UNBREAKABLE COVENANT with the Jews descendents of Isaac. If this so UNBREAKABLE COVENANT is real then why did YHWH establish a new Covenant with the Gentiles Through Jesus?