Gentiles are Israel

Romans 10:12-13 For there is no distinction between Jew and Greek; for the same Lord is Lord of all, abounding in riches for all who call on Him; 13 for “Whoever will call on the name of the Lord will be saved

Romans 11:13-18 But I am speaking to you who are Gentiles. Inasmuch then as I am an apostle of Gentiles, I magnify my ministry, 14 if somehow I might move to jealousy my fellow countrymen and save some of them. 15 For if their rejection is the reconciliation of the world, what will their acceptance be but life from the dead? 16 If the first piece of dough is holy, the lump is also; and if the root is holy, the branches are too.17 But if some of the branches were broken off, and you, being a wild olive, were grafted in among them and became partaker with them of the rich root of the olive tree, 18 do not be arrogant toward the branches; but if you are arrogant, remember that it is not you who supports the root, but the root supports you

Romans 2:28-29 For he is not a Jew who is one outwardly, nor is circumcision that which is outward in the flesh. 29 But he is a Jew who is one inwardly; and circumcision is that which is of the heart, by the Spirit, not by the letter; and his praise is not from men, but from God.

Galatians 3:28-29 There is neither Jew nor Greek, there is neither slave nor free man, there is neither male nor female; for you are all one in Christ Jesus. 29 And if you belong to Christ, then you are Abraham’s descendants, heirs according to promise.

Ephesians 2:16-19 and might reconcile them both in one body to God through the cross, by it having put to death the enmity. 17 And He came and preached peace to you who were far away, and peace to those who were near; 18 for through Him we both have our access in one Spirit to the Father. 19 So then you are no longer strangers and aliens, but you are fellow citizens with the saints, and are of God’s household

Acts 4:12 And there is salvation in no one else; for there is no other name under heaven that has been given among men by which we must be saved.”

Matthew 15:24 But He answered and said, “I was sent only to the lost sheep of the house of Israel.”

Acts 15:8-9 And God, who knows the heart, testified to them giving them the Holy Spirit, just as He also did to us; 9 and He made no distinction between us and them, cleansing their hearts by faith

Jews and Gentiles are BOTH Israel in Christ with no distinction. This means that the New Covenant that Gentiles are a part of is for them 

Hebrews 8:10-12 “For this is the covenant that I will make with the house of Israel. After those days, says the Lord: I will put My laws into their minds, And I will write them on their hearts. And I will be their God, And they shall be My people. 11 “And they shall not teach everyone his fellow citizen, And everyone his brother, saying, ‘Know the Lord,’ For all will know Me, From the least to the greatest of them. 12 “For I will be merciful to their iniquities, And I will remember their sins no more.”

Hebrews 10:15-17   And the Holy Spirit also testifies to us; for after saying, 16 “This is the covenant that I will make with them After those days, says the Lord: I will put My laws upon their heart, And on their mind I will write them,”  He then says, 17 “And their sins and their lawless deeds I will remember no more.”

If there is no difference between Jews and Gentiles, then the New Covenant cannot be with only Jews or Only Gentiles.  The idea that Jews are saved by being Jewish is contrary to Christ. There is no Gentile covenant, only the Covenant with Israel -of which a mixed multitude always was comprised.