Theodoret of Cyrus: Church is All Believers

And he made him head over all things for the Church, which is his body (vv.22-23): Christ the Lord has the position of head, whereas those who believe in him have the position of the body. The fulness of him who fills all in all. By Church he refers to the collection of the faithful; he called it Christ's body and the Father's fullness: he filled it with all kinds of gifts, he dwells in it and walks about in it, according to the inspired text.

- Theodoret of Cyrus (around A.D. 393 to around A.D. 457), Commentary on the Letter to the Ephesians, Chapter 1, in Theodoret of Cyrus, Commentary on the Letters of St. Paul, Volume 2, pp. 37-38 (2001), Robert C. Hill translator.