Romans 11:25

11:25 For I do not want you to be ignorant of this mystery, brothers and sisters, so that you may not be conceited: A partial hardening has happened to Israel until the full number of the Gentiles has come in.

Romans 16:25

16:25 Now to him who is able to strengthen you according to my gospel and the proclamation of Jesus Christ, according to the revelation of the mystery that had been kept secret for long ages,

Ephesians 3:3-9

3:3 that by revelation the divine secret was made known to me, as I wrote before briefly. 3:4 When reading this, you will be able to understand my insight into this secret of Christ. 3:5 Now this secret was not disclosed to people in former generations as it has now been revealed to his holy apostles and prophets by the Spirit, 3:6 namely, that through the gospel the Gentiles are fellow heirs, fellow members of the body, and fellow partakers of the promise in Christ Jesus. 3:7 I became a servant of this gospel according to the gift of God’s grace that was given to me by the exercise of his power. 3:8 To me – less than the least of all the saints – this grace was given, to proclaim to the Gentiles the unfathomable riches of Christ 3:9 and to enlighten everyone about God’s secret plan – a secret that has been hidden for ages in God who has created all things.