We all know that born again believers are saved by grace, that is, that we deserve death; and yet, because God is merciful, He offers salvation to whomsoever will accept His Son (Jn. 1:11-12; Rom. 10:8-13; Eph. 2:8-9; etc.). In Romans 11:1-29, Paul explained that Israel was hindered from recognizing the truth (v. 25), but that once the Gentiles were given the opportunity to accept Jesus, God will save ALL Israel (v. 26)! Again, how can that be? The answer is the same: GRACE!
It will be during the Tribulation that the "blindness" will be removed, and Israel will finally recognize that Jesus was, and always will be, their Messiah. When the Antichrist commits the Abomination of Desolation (Dan. 9:27; 11:31; 12:11; Mt. 24:15; Rev. 13:5-7; etc.), they suddenly realize that the one they had believed to be their Christ, was in fact, the Antichrist! The Spirit of God will bring to their memory the sequence of events in Daniel's prophecy of seventy weeks (9:24-27): the Antichrist will confirm a covenant with them and will break it at a time long AFTER THEIR MESSIAH HAD BEEN KILLED! That means, Jesus was their Messiah; and since the prophecies of His Kingdom were yet to be fulfilled, they will know He will be returning soon! GRACE UPON GRACE!
It is no surprise that Israel will be a part of the Bride; the Old Testament referred to her as God's wife many times. In fact, the Book of Hosea is a picture of God and His unfaithful wife, Israel! While there are some who think God divorced her PERMANENTLY, God's view on divorce over adultery is clearly revealed in Matthew 19:8 which says, "He saith unto them, Moses because of the hardness of your hearts suffered you to put away your wives: but from the beginning it was not so."
God does not have a hardened heart! His bride consists of the Church and Israel!