Yesterday, I watched a debate between Jeff Riddle and James White on Ephesians 3:9.
James White thinks it should be “the plan of the mystery“ instead of “the fellowship of the mystery.”
I am surprised that neither of these debaters brought up Colossians 1:26-27.
Colossians 1:26-27
26 "Even the mystery which hath been hid from ages and from generations, but now is made manifest to his saints:
27 To whom God would make known what is the riches of the glory of this mystery among the Gentiles; which is Christ in you, the hope of glory:"
The fellowship of the mystery is.... Christ in you, who is our hope of glory.
If Christ is in a person, they have fellowship with Him.
So ”Christ in you” is the “fellowship of the mystery” being spoken about in Ephesians 3:9.
In short, the Modern scholars are not aware of all of the Scriptural cross references.
They don't know their Bible, and so they make ridiculous changes that is not supported by the whole counsel of God's Word.