Two Different Oaths
If ancient Israel and the covenant they had with God is as Hebrews describes then these people and their covenant are nothing but shadows.
KJV Hebrews 10:1
1. For the law having a shadow of good things to come, and not the very image of the things, can never with those sacrifices which they offered year by year continually make the comers thereunto perfect.
I read in scripture that Jesus said that we are to be perfect as our Father in heaven.
KJV Matthew 5:48
48. Be ye therefore perfect, even as your Father which is in heaven is perfect.
KJV Hebrews 7:19
19. For the law made nothing perfect, but the bringing in of a better hope did; by the which we draw nigh unto God.
The message of the book of Hebrews was to show that the old covenant can not produce salvation and that all of it was only a shadow of the new covenant in Jesus Christ. I have written before about Abraham; Abraham was a gentile who lived with his father and worshiped idols before God called him. When God called Abraham, Abraham became a Christian because God taught Abraham the gospel and about the son God would have who would be the messiah. In Abraham all the nations of the Earth would be blessed and Jesus was the promised seed of Abraham according to the flesh. The nation of Israel did not exist in Abrahams day and neither did the old covenant God would later make with Israel. There was an oath God swore to Abraham that did not involve the old covenant or the carnal nation of Israel. Abraham had no inheritance in the land that God would later give to his carnal descendents.
KJV Acts 7:3-5
3. And said unto him, Get thee out of thy country, and from thy kindred, and come into the land which I shall shew thee.
4. Then came he out of the land of the Chaldaeans, and dwelt in Charran: and from thence, when his father was dead, he removed him into this land, wherein ye now dwell.
5. And he gave him none inheritance in it, no, not so much as to set his foot on: yet he promised that he would give it to him for a possession, and to his seed (The glorified saints)after him, when as yet he had no child.
Abraham was promised an inheritance far greater than the nation of Israel.
KJV Romans 4:13
13. For the promise, that he should be the heir of the world, was not to Abraham, or to his seed, through the law, but through the righteousness of faith.
Abraham will be in the first resurrection, he is one of the 144,000 of Gods elect saints and is of the first stage of the church, the ancient saints listed in Hebrews 11 and one of the two loaves of leavened bread in Leviticus 23. The inheritance of the saints is to be a joint heir with Jesus. They are the first fruits to God and the lamb.
Abraham had no part in carnal Israel or the old covenant that would come 430 years later. The old covenant did not void the oath God swore to Abraham or transfer the oath to the carnal nation of Israel.
KJV Galatians 3:6-18
6. Even as Abraham believed God, and it was accounted to him for righteousness.
7. Know ye therefore that they which are of faith, the same are the children of Abraham.
8. And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed.
9. So then they which be of faith are blessed with faithful Abraham.
10. For as many as are of the works of the law are under the curse: for it is written, Cursed is every one that continueth not in all things which are written in the book of the law to do them.
11. But that no man is justified by the law in the sight of God, it is evident: for, The just shall live by faith.
12. And the law is not of faith: but, the man that doeth them shall live in them.
13. Christ hath redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is every one that hangeth on a tree:
14. That the blessing of Abraham might come on the Gentiles through Jesus Christ; that we might receive the promise of the Spirit through faith.
15. Brethren, I speak after the manner of men; Though it be but a man's covenant, yet if it be confirmed, no man disannulleth, or addeth thereto.
16. Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ.
17. And this I say, that the covenant, that was confirmed before of God in Christ, the law, which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect.
18. For if the inheritance be of the law, it is no more of promise: but God gave it to Abraham by promise.
What Paul is saying here is that ancient Israel under the old covenant was never an heir to the promises God made to Abraham. In order for anyone to receive the promises they must come to Abrahams seed, Jesus, who is the heir and we then joint heirs with him by faith.
The blessing and cursing under the law was an entirely different oath that did not in any way alter the oath God swore to Abraham. Those under this old covenant oath were under a curse that can only be removed if they come to Jesus. So, until carnal Israel does come to Christ they are not heirs with the church, with those of the faith of Abraham. The carnal Israelites then and today are not the heirs of the oath God swore to Abraham because the oath did not come through the law but by promise. Abraham and all the saints will when Jesus returns inherit the Earth and be a blessing to all nations.
The oath God made with Abraham and the oath God made with carnal Israel are completely different oaths that had nothing to do with each other. Carnal Israel and the old covenant was only a shadow of the oath God swore to Abraham. Israel made a covenant of death but Abrahams was to life. Under the law Israel inherited nothing because due to disobedience lost what they had been given. The only way for carnal Israel to ever have hope to share in the oath God swore to Abraham is to do what Abraham did, have faith and become a Christian.
Comparing The Two Covenants
As mentioned the old covenant was only a shadow of the new covenant. We are familiar with many of the shadow types; Aaron as a type of Jesus, all the sacrifices typing that of Jesus and so on. The one thing both covenants had in common was that obedience was required to receive the promises each contained. The old covenant oath had blessings for obedience and curses for disobedience. Carnal Israel did not even meet the requirement to have the blessings under the law and because of idolatry the entire nation fell under the curse. The southern kingdom of Judah was only permitted to return from captivity in Babylon because Jesus had to be born in Judea to fulfill prophecy. According to the condition of obedience Israel failed and is to this day under the curse of the law. It cannot be that Israel could be blessed and cursed at the same time; this is very important to understand and since they are yet in disobedience to the covenant they are yet cursed with no blessings from God at all. Remember, the blessings under the law were not the blessings of Abraham, the two oaths were not the same. The new covenant requires obedience to the gospel and living by faith and love while shielded by grace. The new covenant provides repentance from sin or those times we break the covenant and will forgive us. The old covenant will not forgive and provides no repentance therefore once Israel sinned and forsook God the curse overtook them. Scripture says that God divorced Israel, cast them out of the land and no longer calls them His people. Carnal Israel is totally cut off from God and they killed any hope of being reconnected in this age when they killed Jesus. God has not forever cast off carnal Israel and will in the millennium convert them to Christianity. The only way anyone can be an heir to the oath God swore to Abraham is to become a Christian.