Rom 10:20-21, Rom 9:24-26, Mt 23:37, Lk 13:34, Acts 7:51-52, 1 Thess 2:15-16

In the Old Testament, God said that He would visit the Gentiles who did not seek Him. (Isa 65:1-2)

Isa 65:1 I am sought of them that asked not for me; I am found of them that sought me not: I said, Behold me, behold me, unto a nation that was not called by my name. 2 I have spread out my hands all the day unto a rebellious people, which walketh in a way that was not good, after their own thoughts;

The Israelites disobeyed God, so God went to the Gentiles and made them His people. (Romans 10:20-21, Romans 9:24-26)

Romans 10:20 But Esaias is very bold, and saith, I was found of them that sought me not; I was made manifest unto them that asked not after me. 21 But to Israel he saith, All day long I have stretched forth my hands unto a disobedient and gainsaying people.

Romans 9:24 Even us, whom he hath called, not of the Jews only, but also of the Gentiles? 25 As he saith also in Osee, I will call them my people, which were not my people; and her beloved, which was not beloved. 26 And it shall come to pass, that in the place where it was said unto them, Ye are not my people; there shall they be called the children of the living God.

The people of Israel who had killed the prophets in the Old Testament did not want the Christ to protect and save them, but killed that Christ. (Matthew 23:37, Luke 13:34, Acts 7:51-52, Thessalonians 2:15-16)

Matthew 23:37 O Jerusalem, Jerusalem, thou that killest the prophets, and stonest them which are sent unto thee, how often would I have gathered thy children together, even as a hen gathereth her chickens under her wings, and ye would not!

Luke 13:34 O Jerusalem, Jerusalem, which killest the prophets, and stonest them that are sent unto thee; how often would I have gathered thy children together, as a hen doth gather her brood under her wings, and ye would not!

Acts 7:51 Ye stiffnecked and uncircumcised in heart and ears, ye do always resist the Holy Ghost: as your fathers did, so do ye. 52 Which of the prophets have not your fathers persecuted? and they have slain them which shewed before of the coming of the Just One; of whom ye have been now the betrayers and murderers:

1 Thessalonians 2:15 Who both killed the Lord Jesus, and their own prophets, and have persecuted us; and they please not God, and are contrary to all men: 16 Forbidding us to speak to the Gentiles that they might be saved, to fill up their sins alway: for the wrath is come upon them to the uttermost.