In scripture, there are four major covenants which have to do with God’s relationship with his people.
1. The promises God made to Abraham, which are confirmed in Christ. (Galatians 3)
2. The Law of Moses (aka the old covenant). This was Israel’s covenant in the flesh.
3. The New Covenant. This covenant replaced the old covenant (Israel’s covenant in the flesh). This covenant was given to the house of Israel and the house of Judah (see Hebrews 8). Those among the people of Israel, who believe the gospel are given this covenant, and Gentiles who believe the gospel are grafted with them as the Israel of God. The seal of this covenant is not physical circumcision, but circumcision of the heart instead.
According to Paul, those who are united in Christ (Jews and Gentiles) are the true Israel in the eyes of God.
In Galatians 6: 12-16 Paul says the following:
As many as desire to make a fair shew in the flesh, they constrain you to be circumcised; only lest they should suffer persecution for the cross of Christ. For neither they themselves who are circumcised keep the law; but desire to have you circumcised, that they may glory in your flesh. But God forbid that I should glory, save in the cross of our Lord Jesus Christ, by whom the world is crucified unto me, and I unto the world. For in Christ Jesus neither circumcision availeth any thing, nor uncircumcision, but a new creature. And as many as walk according to this rule, peace be on them, and mercy, and upon the Israel of God.
Paul applies the title “the Israel of God” to those who have been reborn in Christ and not as a reference to ethnic Jews.
If the Israel of God mentioned in Galatians 6 were a reference to the ethnic Jews, then the cross has been made of no effect, for there would be two covenant families of God and not one. Furthermore, if the Israel of God is a reference to born again ethnic Jews, then there is still a dividing wall between Jews and Gentiles, and again, the cross would be made of no effect.
In view of all Paul has written in Galatians, the Israel of God can only refer to believers in the Messiah, who, in the fullest sense of the word are Abraham’s seed and heirs according to the promise. Paul has made it abundantly clear that, in Christ Jesus, neither circumcision (which was the mark of Jewish national identity under the law) nor uncircumcision mean anything. What matters is being a new creature, and those who are such are the true Israel in God’s sight.
In Ephesians 2 Paul tells us that the uncircumcised in the flesh are no longer strangers to the “commonwealth of Israel,” but have been made nigh to the covenants of promise through the blood of Christ. Jesus Christ has abolished the dividing wall which separated Jews and Gentiles, and now the two have become one in Christ.
Jews who reject the gospel are cut off from being the people of God just as the scriptures declares: For Moses truly said unto the fathers, A prophet shall the Lord your God raise up unto you of your brethren, like unto me; him shall ye hear in all things whatsoever he shall say unto you.And it shall come to pass, that every soul, which will not hear that prophet, shall be destroyed from among the people. ~ Acts 3:22-23
Gentiles who reject lost the gospel, are lost in their sins.
4. The oath God made with David. God promised David that he would raise up one of his descendants, who would be the Messiah, to reign as King forever upon his throne.
David was the great King of Israel after the flesh. Jesus Christ is the King of Israel being exalted at the right hand of God.
When the angel Gabriel appeared to Mary he said concerning Jesus, “He shall be great, and shall be called the Son of the Highest: and the Lord God shall give unto him the throne of his father David.“ ~ Luke 1:32
In Acts 2, Peter interprets the resurrection and exaltation of Jesus at the right hand of God as the fulfillment of the scriptures that the Messiah would reign from the throne of David.
Therefore being a prophet, and knowing that God had sworn with an oath to him, that of the fruit of his loins, according to the flesh, he would raise up Christ to sit on his throne; he seeing this before spake of the resurrection of Christ, that his soul was not left in hell, neither his flesh did see corruption. This Jesus hath God raised up, whereof we all are witnesses. Therefore being by the right hand of God exalted, and having received of the Father the promise of the Holy Ghost, he hath shed forth this, which ye now see and hear. For David is not ascended into the heavens: but he saith himself, the Lord said to my Lord, sit on my right hand, until I make thy foes thy footstool. Therefore let all the house of Israel know assuredly, that God hath made the same Jesus, whom ye have crucified, both Lord and Christ. ~ Acts 2:30-36
The apostle Paul referred to this as “the sure mercies of David.”
And we declare unto you glad tidings, how that the promise which was made unto the fathers, God hath fulfilled the same unto us their children, in that he hath raised up Jesus again; as it is also written in the second psalm, Thou art my Son, this day have I begotten thee. And as concerning that he raised him up from the dead, now no more to return to corruption, He said on this wise, I will give you the sure mercies of David. Wherefore he saith also in another psalm, Thou shalt not suffer thine Holy One to see corruption. For David, after he had served his own generation by the will of God, fell on sleep, and was laid unto his fathers, and saw corruption: But he, whom God raised again, saw no corruption. ~ Acts 13:13-37
How do these covenants have a direct affect on the lives of Christians?
1. The blessing of Abraham, which is justification through faith in Jesus, is the inheritance of every believer. Through our faith in Jesus, we are members of the family of Abraham, which is the family of God.
2. Being in the family of God, no longer means being grafted into the physical nation of Israel, as was the case under the Law. Under Moses, physical Israel was God’s covenant people, and being in covenant with God meant that one had to be a citizen of national Israel. This is no longer the case. The family of God consists of people from every nation, for God fulfilled his promise to Abraham, to make him the father of many nations, through his Son Jesus Christ, who is the promised seed of Abraham.
3. In Christ we become partakers of a new covenant. This new covenant was given to the house of Israel and the house of Judah. In this covenant, believing Gentiles are grafted in with believing Jews and become fellow heirs with them as the Israel of God.
Paul uses the language of “the Israel of God” in Galatians 6 in conjunction with those who are circumcised, not with physical circumcision, but through the putting to death of the old man through the power of the Cross. The apostle Peter says, “ye are a chosen generation, a royal priesthood, an holy nation, a peculiar people; that ye should shew forth the praises of him who hath called you out of darkness into his marvellous light…” ~ 1 Peter 2:9
4. Christ is the exalted King of glory, and we are his ambassadors as in a foreign land. His Kingdom is not of this world, but through us, his power and Kingdom saves people from the darkness in this world. We are his messengers and representatives, and his Kingdom reigns over darkness through his power, in his people, who are his ambassadors in this world. One day, the King of glory will return and take over this world.