The Apostle Paul
Ephesians 3:9ESV·traditional attribution

and to bring to light for everyone what is the plan of the mystery hidden for ages in God, who created all things,

John Calvin Reformed @genevareformer

9. What is the fellowship of the mystery. The publication of the gospel is called a fellowship, because it is the will of God that his purpose, which had formerly been hidden, shall now be shared by men. There is an appropriate metaphor in the words φωτίσαι πάντας, to enlighten all men, — conveying the thought, that, in his apostleship, the grace of God shines with the brightness of noon-day.

Matthew Henry Presbyterian @wholebiblehenry

Here we have the account which Paul gives the Ephesians concerning himself, as he was appointed by God the apostle of the Gentiles. I. We may observe that he acquaints them with the tribulations and sufferings which he endured in the discharge of that office, Eph 3:1. The first clause refers to the preceding chapter, and may be understood either of these two ways: - 1.

Commenting on Ephesians 3:1-13

John Gill Reformed Baptist @doctorgill

And to make all men see what is the fellowship of the mystery,.... Or "the dispensation of the mystery" as the Complutensian, and several copies, and the Vulgate Latin and Syriac versions, read. The mystery is the Gospel; the fellowship of it is the communication of grace by it, a participation of the truths and doctrines of it, communion with Father, Son, and Spirit, which...