Chapter 8.
83 “If so be,” he says, “we suffer with Him, that we may be also glorified together.” If we then shall be glorified together with Christ through the Spirit, how do we refuse to admit that the Spirit Himself is glorified together with Christ? Do we dissociate the life of Christ and of the Holy Spirit when the Spirit says that we shall live together with the Son of God? For the Apostle says: “If we be dead with Christ we believe that we shall also live with Him;” and then again: “For if we suffer with Him we shall also live with Him, and not only shall we live with Him, but shall be also glorified with Him, and not only be glorified but shall also reign with Him.”
84. No division, then, is implied in those particles, for each is a particle of conjunction. And lastly, we often find in holy Scripture the one inserted and the other understood, as it is written: “I will enter into Your house in whole burnt-offerings,” that is, “with whole burnt-offerings;” and in another place: “He brought them forth in silver and gold,” that is, “with silver and gold.” And elsewhere the Psalmist says: “Will You not go forth with us in our hosts?” for that which is really meant, “with our hosts.” So, then, in the use of the expression no lessening of honour can be implied, and nothing ought to be deduced derogatory to the honour of the Godhead, it is necessary that with the heart man should believe unto righteousness, and that out of the faith of the heart confession should be made in the mouth unto salvation. But they who believe not with the heart spread what is derogatory with their mouth.
Source: On the Holy Spirit (New Advent)