The Abrahamic covenant is to Abraham and his descendants:
"and God said to him, 4 “As for me, this is my covenant with you: You will be the father of many nations. 5 No longer will you be called Abram; your name will be Abraham, for I have made you a father of many nations. 6 I will make you very fruitful; I will make nations of you, and kings will come from you. 7 I will establish my covenant as an everlasting covenant between me and you and your descendants after you for the generations to come, to be your God and the God of your descendants after you. 8 The whole land of Canaan, where you now reside as a foreigner, I will give as an everlasting possession to you and your descendants after you; and I will be their God.”"
Now the promises were made to Abraham and to his offspring. It does not say, “And to offsprings,” referring to many, but referring to one, “And to your offspring,” who is Christ. - Gal 3:16
And do not presume to say to yourselves, ‘We have Abraham as our father,’ for I tell you, God is able from these stones to raise up children for Abraham. - Matt 3:9
For no one is a Jew who is merely one outwardly, nor is circumcision outward and physical. 29 But a Jew is one inwardly, and circumcision is a matter of the heart, by the Spirit, not by the letter. His praise is not from man but from God. -
It is not as though God’s word had failed. For not all who are descended from Israel are Israel. 7 Nor because they are his descendants are they all Abraham’s children. On the contrary, “It is through Isaac that your offspring will be reckoned.” 8 In other words, it is not the children by physical descent who are God’s children, but it is the children of the promise who are regarded as Abraham’s offspring. - Romans 9:6-8
even us, whom he also called, not only from the Jews but also from the Gentiles? 25 As he says in Hosea:
“I will call them ‘my people’ who are not my people;
and I will call her ‘my loved one’ who is not my loved one,
and,
“In the very place where it was said to them,
‘You are not my people,’
there they will be called ‘children of the living God. - Romans 9:24-28.
So the all those of faith are children of the promise to Abraham, the nation of Israel came about under the mosaic covenant.
By faith Abraham, when called to go to a place he would later receive as his inheritance, obeyed and went, even though he did not know where he was going. 9 By faith he made his home in the promised land like a stranger in a foreign country; he lived in tents, as did Isaac and Jacob, who were heirs with him of the same promise. 10 For he was looking forward to the city with foundations, whose architect and builder is God. 11 And by faith even Sarah, who was past childbearing age, was enabled to bear children because she considered him faithful who had made the promise. 12 And so from this one man, and he as good as dead, came descendants as numerous as the stars in the sky and as countless as the sand on the seashore.
13 All these people were still living by faith when they died. They did not receive the things promised; they only saw them and welcomed them from a distance, admitting that they were foreigners and strangers on earth. 14 People who say such things show that they are looking for a country of their own. 15 If they had been thinking of the country they had left, they would have had opportunity to return. 16 Instead, they were longing for a better country—a heavenly one. Therefore God is not ashamed to be called their God, for he has prepared a city for them. - Hebrew 11:8ff
And all of Abraham's seed can look forward to the eternal promise Gen 17:8:
Then I saw “a new heaven and a new earth,” for the first heaven and the first earth had passed away, and there was no longer any sea. 2 I saw the Holy City, the new Jerusalem, coming down out of heaven from God, prepared as a bride beautifully dressed for her husband. - Revelation 21:1-2.