Ephesians 3:9,10
And to make all men see what is the fellowship of the mystery, which from the beginning of the world has been hid in God, who created all things by Jesus Christ:
Torrey's Topical Textbook—AKJV

1 Timothy 3:16
And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached to the Gentiles, believed on in the world, received up into glory.
Torrey's Topical Textbook—AKJV

1 Peter 1:12
To whom it was revealed, that not to themselves, but to us they did minister the things, which are now reported to you by them that have preached the gospel to you with the Holy Ghost sent down from heaven; which things the angels desire to look into.
Torrey's Topical Textbook—AKJV