Ephesians 3:2-3, 5-6

if indeed you have heard of the stewardship of God’s grace which was given to me for you; that by revelation there was made known to me the mystery, as I wrote before in brief.

which in other generations was not made known to the sons of men, as it has now been revealed to His holy apostles and prophets in the Spirit; to be specific, that the Gentiles are fellow heirs and fellow members of the body, and fellow partakers of the promise in Christ Jesus through the gospel