Chapter 11.
81 It makes, then, nothing against our argument that God is worshipped in Spirit, for the Spirit also is worshipped. Although if we consider the words themselves, what else ought we to understand in the Father, the Son, and the Holy Spirit, but the unity of the same power. For what is “must worship in Spirit and in truth”? If, however, you do not refer this to the grace of the Spirit, nor the true faith of conscience; but, as we said, personally (if indeed this word person is fit to express the Divine Majesty), you must take it of Christ and of the Spirit.
82. What means, then, the Father is worshipped in Christ, except that the Father is in Christ, and the Father speaks in Christ, and the Father abides in Christ. Not, indeed, as a body in a body, for God is not a body; nor as a confused mixture [confusus in confuso], but as the true in the true, God in God, Light in Light; as the eternal Father in the co-eternal Son. So not an ingrafting of a body is meant, but unity of power. Therefore, by unity of power, Christ is jointly worshipped in the Father when God the Father is worshipped in Christ. In like manner, then, by unity of the same power the Spirit is jointly worshipped in God, when God is worshipped in the Spirit.
83. Let us investigate the force of that word and expression more diligently, and deduce its proper meaning from other passages. “You have,” it is said, “made them all in wisdom.” Do we here understand that Wisdom was without a share in the things that were made? But “all things were made by Him.” And David says: “By the Word of the Lord were the heavens established.” So, then, he himself who calls the Son of God the maker even of heavenly things, has also plainly said that all things were made in the Son, that in the renewal of His works He might by no means separate the Son from the Father, but unite Him to the Father.
84. Paul, too, says: “For in Him were all things created in the heavens and in the earth, visible and invisible.” Does he, then, when he says, “in Him,” deny that they were made through Him? Certainly he did not deny but affirmed it. And further he says in another place: “One Lord Jesus, through Whom are all things.” In saying, then, “through Him,” has he denied that all things were made in Him, through Whom he says that all things exist? These words, “in Him” and “with Him,” have this force, that by them is understood one and like in all respects, not contrary. Which he also made clear farther on, saying: “All things have been created through Him and in Him;” for, as we said above, Scripture witnesses that these three expressions, “with Him,” and “through Him,” and “in Him,” are equivalent in Christ. For you read that all things were made through Him and in Him.
85. Learn also that the Father was with Him, and He with the Father, when all things were being made. Wisdom says: “When He was preparing the heavens I was with Him, when He was making the fountains of waters.” And in the Old Testament the Father, by saying, “Let Us make,” showed that the Son was to be worshipped with Himself as the Maker of all things. As, then, those things are said to have been created in the Son, of which the Son is received as the Creator; so, too, when God is said to be worshipped in truth by the proper meaning of the word itself often expressed after the same manner it ought to be understood, that the Son too is worshipped. So in like manner is the Spirit also worshipped because God is worshipped in Spirit. Therefore the Father is worshipped both with the Son and with the Spirit, because the Trinity is worshipped.
Source: On the Holy Spirit (New Advent)