The Apostle Paul
Ephesians 1:23BSB·traditional attribution

which is His body, the fullness of Him who fills all in all.

John Calvin Reformed @genevareformer

23. The fullness of him that filleth all in all. This is the highest honor of the Church, that, until He is united to us, the Son of God reckons himself in some measure imperfect. What consolation is it for us to learn, that, not until we are along with him, does he possess all his parts, or wish to be regarded as complete!

Matthew Henry Presbyterian @wholebiblehenry

We have come to the last part of this chapter, which consists of Paul's earnest prayer to God in behalf of these Ephesians. We should pray for the persons for whom we give thanks. Our apostle blesses God for what he had done for them, and then he prays that he would do more for them.

Commenting on Ephesians 1:15-23

John Gill Reformed Baptist @doctorgill

Which is his body,.... That is, which church is the body of Christ; as an human body is but one, consisting of various members, united to each other, and set in an exact proportion and symmetry, and in a proper subservience to one another, and which must be neither more nor fewer than they are; so the church of Christ is but one general assembly...