How could Christ make it possible for Gentiles to be heirs to the PROMISES MADE TO Israel?
Christ, the Heir of Abraham
The promise of eternal inheritance of the earth was unconditionally made to Abraham and his "seed" (Gen. 26:3). But Abraham died without inheriting the promises (Heb. 11:13). It remained for Jesus Christ the ONE Heir who was without sin -- the promised "seed" through the lineage of Abraham--to inherit the promises (Gal. 3:16).
Jesus came in the flesh to confirm the promises made to the fathers (Rom. 15:8). He also was the minister of a new testament or will by which he would bequeath His entire inheritance to His heirs in case of death. Remember the NEW Testament contained the promises of ETERNAL INHERITANCE, not the old (Heb. 9:15).
Christ's testament or will did not have any force until his death. "For a testament is of force AFTER men are dead" (Heb. 9:17). When Christ died, then His heirs had the right to the eternal inheritance made possible through the Holy Spirit which imparts eternal life. But who are the heirs of Christ?
No one is Christ's UNLESS one believes, repents and is baptized (Acts 2:38; Gal. 3:27). so you can become an heir of Christ if you fulfill this condition and receive the Holy Spirit which puts - immerses- you into the church whether you are Israelite or Gentile (I Cor. 12:13). We are Christ's because Christ BOUGHT us by giving His life in our stead to pay for our sins (I Cor. 6:20).
New Covenant
Not Yet Completed
Christ is the Mediator of the new covenant (Heb. 8:6). According to the prophecy of Daniel 9:27, Christ has not yet completed His work of confirming the covenant. The covenant must yet be completed IN THE FUTURE - 'For this is the covenant that I WILL make with the house of Israel AFTER THOSE DAYS, saith the Lord; I WILL put my laws into their mind and write them in their hearts' (Heb. 8:10; Jer. 31: 31-34).
The new covenant will not be made with fleshy, carnal Israelites who can still sin - it will correct that fault. This time it will be made with Spirit-born Israelites who have been forgiven their sins and who have God's laws written in their minds and hearts so they can't sin and break the covenant. The apostle John reveals that it is only at the resurrection when we are BORN AGAIN - composed of a spirit body, just like Christ and the Father that we won't be able to sin because we will have God's nature permanently implanted in us (I John 3:9). Jesus told Nicodemus that we must be born again of the Spirit before we can inherit the kingdom and gain eternal life (John 3: 1-6).
Understand that the new testament or will of Jesus Christ has been in force since his death. But his testament or will has conditions, which we must meet before we can inherit the promises. The Greek word for 'testament' also means 'covenant'. Since the new testament involves our agreement to fulfill these conditions, it also becomes a covenant and that new covenant will not be confirmed with us. We won't INHERIT THE PROMISES UNTIL we are first made immortal and have God's nature so we can't sin (II Peter 1:4).
New Covenant
A Marriage Agreement
All that the scripture says concerning Israel and the promises under the new testament pertains to the church. It is the church that is Israel begotten and soon to be born of the Spirit as spirit sons of God (Acts 26:6-7). Under the old covenant Israel could have become a kingdom of priests (Ex. 19:6). Under the new covenant the church will become a kingdom of priests governing the physical nation of Israel (I Pet. 2:9; Rev. 5:10; Acts I 6).
As the church is Israel Abraham's seed and heirs of the promise - then it is the church with whom the new covenant will finally be made. But we read in II Cor. 11:2 and Eph. 5:32 that Christ Jesus at His second coming will marry the church, which is now his espoused bride. Therefore, the new covenant will be ANOTHER MARRIAGE AGREEMENT! Christ will be the husband and the church will become His wife. Remember that the God of the Old Testament was the husband of ancient Israel. Under the old covenant Israel could never remarry her husband once the divorce was given and she was defiled by relationships with heathen gods. The Lord of the Old Testament - NOT the Father - but the Word who became Jesus was born into human flesh to DIE so that Israel would be free to remarry. That's why we read in Rev. 19:7 that before the coming marriage between Christ and the church takes place it will be said: "The marriage of the Lamb is come, and HIS WIFE (not bride) hath made herself ready." This could not be said of the church unless it was Jesus and not the Father to whom Israel had once been married. Besides, no man has ever seen the Father at any time (Jn. 1:18) and Moses saw the God of the Old Testament from behind when he was receiving the Ten Commandments on Mt. Sinai.