This mystery of salvation for the Gentiles was revealed through Jesus Christ. Gentiles are now heirs with Jews (Ephesians 3:3-6). This had been hidden from all past generations (2 Peter 1:21).
The Jews knew to look for their Messiah but they believed it was to defeat the Romans, set them free, and set up God’s kingdom, not to bring equality between them and Gentiles.
Set apart

What had God told them?
Isaiah 42:6 God says the Messiah will come as a covenant to Israel and a Light to the Gentile nations. There was no detailed description as to how this would happen, so the Jews filled in the details, and history keeps repeating itself even today. There are still things no one understands and the same thing is done, man’s reasoning is added to scripture.
The Jews believed their being given the law by Moses and Abraham being their father is what set them apart. But Jesus, Who is God, came and began to say it is time for change (this is now).
Jesus voiced this by saying “I have come to seek and save the lost”. He read from Isaiah which says “The Spirit of the Lord [is] upon Me, because He has anointed Me [the Anointed One, the Messiah] to preach the good news (the Gospel) to the poor; He has sent Me to announce release to the captives and recovery of sight to the blind, to send forth as delivered those who are oppressed (who are downtrodden, bruised, crushed, and broken down )…”
Jesus told a parable about two men coming to pray. One came and gave himself a glowing review of how good he is and does everything right. The other would not even look up to heaven but could only cry out to God about his sinfulness. Jesus said, this person was justified before God. Jesus Is saying God is looking at what motivates the outward actions, but they did not recognize Him or hear Him because He did not fit their mould A Christian who seeks God with ALL their heart and mind will be shown the Truth according to God. For a disciple of Jesus Christ this is the greatest knowledge and wisdom to be possessed.