Well, what are those promises? Why does that matter?
Think about it. There’s no reason that God should grant Gentiles salvation by faith. That promise was made to Abraham and his descendants. To invite the Gentiles in is to give them rights of inheritance that they don’t own. They inherit nothing from Abraham since they aren’t genetic descendants of Abraham.
Just so, when God chose Israel as his “treasured possession” and granted them sonship, he did that for Israel in contrast to the surrounding nations. Indeed, one of the points often made in Deu is that God has a special, unique relationship with Israel.
(Deu 4:5-8 ESV) 5 See, I have taught you statutes and rules, as the LORD my God commanded me, that you should do them in the land that you are entering to take possession of it. 6 Keep them and do them, for that will be your wisdom and your understanding in the sight of the peoples, who, when they hear all these statutes, will say, ‘Surely this great nation is a wise and understanding people.’ 7 For what great nation is there that has a god so near to it as the LORD our God is to us, whenever we call upon him? 8 And what great nation is there, that has statutes and rules so righteous as all this law that I set before you today?
(Deu 7:6-8 ESV) “For you are a people holy to the LORD your God. The LORD your God has chosen you to be a people for his treasured possession, out of all the peoples who are on the face of the earth. 7 It was not because you were more in number than any other people that the LORD set his love on you and chose you, for you were the fewest of all peoples, 8 but it is because the LORD loves you and is keeping the oath that he swore to your fathers, that the LORD has brought you out with a mighty hand and redeemed you from the house of slavery, from the hand of Pharaoh king of Egypt.
If you were raised on passages such as this one, you’d correctly conclude that Israel has a unique relationship with YHWH.
So how would you react upon seeing the Gentiles invited in? How could it be that the uncircumcised, unclean Gentiles would also become God’s treasured possession? Loved by YHWH out of all the peoples who are on the face of the earth?
For a Jew, to see the Gentiles enter the Kingdom was unthinkable, unimaginable. And yet Paul exults in this. He finds it grounds for celebration! It’s not that God has rejected Israel, but rather than the blessings of being Israel have been extended. Israel loses nothing and the Gentiles gain … everything.
So re-read Eph 1 from this perspective —
(Eph 1:3-6 ESV) Blessed be the God and Father of our Lord Jesus Christ, who has blessed us [Jews and Gentiles] in Christ with every spiritual blessing in the heavenly places, 4 even as he chose us [Jews and Gentiles] in him before the foundation of the world, that we should be holy and blameless before him. In love 5 he predestined us [Jews and Gentiles] for adoption as sons through Jesus Christ, according to the purpose of his will, 6 to the praise of his glorious grace, with which he has blessed us in the Beloved.
The entire covenant system has been fulfilled. More than that: transformed and transcended. What was once true of only the Jews is now true of all who believe in Jesus. No longer is race a barrier. Descent from Abraham no longer excludes. Faith opens the heavens to receive all who believe.
(Eph 1:7-10 ESV) 7 In him we have redemption through his blood, the forgiveness of our trespasses, according to the riches of his grace, 8 which he lavished upon us, in all wisdom and insight 9 making known to us the mystery of his will, according to his purpose, which he set forth in Christ 10 as a plan for the fullness of time, to unite all things in him, things in heaven and things on earth.
The forgiveness promised by Jer 31:31 ff (speaking of the new covenant) has been opened to all who believe in Jesus by way of the cross. As a result, we can see God’s destiny coming true. We can see God defeating his enemies and heaven and earth being joined (as will happen fully when Jesus returns but is beginning even now).
(Eph 1:11-12 ESV) 11 In him we have obtained an inheritance, having been predestined according to the purpose of him who works all things according to the counsel of his will, 12 so that we who were the first to hope in Christ might be to the praise of his glory.
God has now given an inheritance both to the Jews and Gentiles. God had always planned for this moment to come, and so it was certain to come, but we are blessed to live in a time when we can see the fulfillment of God’s intentions.
The Jews were the first to accept the Messiah, and those who did bring praise to God as others find Jesus through them.
(Eph 1:13-14 ESV) 13 In him you also, when you heard the word of truth, the gospel of your salvation, and believed in him, were sealed with the promised Holy Spirit, 14 who is the guarantee of our inheritance until we acquire possession of it, to the praise of his glory.
The Gentiles responded to the preaching of the gospel, and so they also received the Spirit, demonstrating that God had opened Israel to those not born of Abraham. The presence of the Spirit among the Gentiles guarantees them God’s adoption and their inheritance.
You see, to be added to Israel is everything. For us Gentiles, it’s the only path to forgiveness and to the new heavens and new earth. The only promises that matter are the promises given to the Jews — and into which we’ve been adopted by God.