“For the gifts and calling of God are without repentance.” Romans 11:29 (KJB)
In chapters 9 – 11 of Romans the apostle Paul has spoken of his nation of people from which he was born, the Hebrews. They have been a people whose eyes have been blinded to the truth of who Jesus is. Even the great apostle was blinded to that truth until the Lord Jesus Himself put him face down on the ground on his way to Damascus to bring back Christians for trial and death (Acts 9).
Now, there are many who tell us that God is finished with the Jewish people. Reading this verse alone (11:29) should be ample evidence that God does not go back on His promises. If not read the whole of chapter 11. If that does not suit your appetite then read chapters nine through eleven thoroughly. If you are still not satisfied read the Old Testament through.
The Promises of God to Israel are irrevocable. They will not be recalled; because God does not recall His promises.
God will finish His work with Israel when He has taken the Church to her reward (“…the fulness of the Gentiles be come in”).
The Christian should be able to rejoice in the fact of this irrevocable promise of God. Knowing this gives us the assurance that what He has began in us He is able to complete as well (Philippians 1:6).
The death, burial, and resurrection of Jesus Christ is an irrevocable promise of God, that whosoever believes on Him will not perish, but will have everlasting life.