It is true that God made Abraham a father of many nations (Gen 17:4-6), and indeed he bore more than one son. However, it is also true that the son of the promise was Isaac and the promise was again reconfirmed to Isaac’s son, Jacob (Israel – Gen 32:28).
Therefore, in a strictly literal and legalistic sense, God’s covenant was with the descendants of Israel (Jacob – see above), despite that other nations also came from Abraham. By the way, you may be aware that Arabs claim descent from Ishmael and were/are, therefore, brethren with the descendants of Isaac and Israel, the Israelites.
But Ishmael was born of a mistake, a lack of faith or misunderstanding by Abraham, which is probably why in the end he and his mother got sent away, probably to protect the promised child of Sarah and, more importantly, to protect the promise God had made. Not much significance attaches, also, to the other children that Abraham subsequently had. I should mention, in passing, that God did not abandon Ishmael, as he blessed and protected him (Gen 21:13-20).
It would, therefore, be dishonest of me (indeed, probably of anyone) to hang onto the fact that Abraham was/is a father of many nations and to use that to attempt to deprive Israel/Jews of their special old covenant status as the descendants of Jacob/Israel, the son of the son of the promise. You may notice, as an aside, that Isaac was not the first born son of Abraham and neither was Israel (and by the way, neither was Abel, the brother of Cain); however, God blessed them according to His will and plan as God, regardless of their status in the family hierarchy!
Therefore, the spiritual approach taken by Apostle Paul, which I dealt with in my first ‘paper’, is much richer and it overcomes and trumps the legalistic approach.
To conclude. My view, therefore, does not negate nor does it minimise the old covenant. I confirm it. Having done so, however, I argue that that old covenant was superseded by a new covenant, which came/comes about through the birth, death and resurrection of another son of the promise, Jesus. Indeed, one may arguably also trace this promise to Abraham. The Angel told Abraham that, “In your seed all the nations of the earth shall be blessed…” (Gen 22:18). I would posit that this message was/is a foretelling of Christ, through whom (the seed of Abraham) all the nations of the earth shall be/have been blessed.
