34 By all these proofs, and by more which have been passed over, is the personal, and sanctifying, and effectual power of the Holy Ghost established for those who can understand; for the time would fail me in my discourse if I wished to quote what yet remains concerning the Holy Ghost from the fourteen Epistles of Paul, wherein he has taught with such variety, completeness, and reverence. And to the power of the Holy Ghost Himself it must belong, to grant to us forgiveness for what we have omitted because the days are few, and upon you the hearers to impress more perfectly the knowledge of what yet remains; while from the frequent reading of the sacred Scriptures those of you who are diligent come to understand these things, and by this time, both from these present Lectures, and from what has before been told you, hold more steadfastly the Faith in “One God the Father Almighty; and in our Lord Jesus Christ, His Only-Begotten Son; and in the Holy Ghost the Comforter.”
Though the word itself and title of Spirit is applied to Them in common in the sacred Scriptures,— for it is said of the Father, God is a Spirit, as it is written in the Gospel according to John; and of the Son, A Spirit before our face, Christ the Lord, as Jeremias the prophet says; and of the Holy Ghost, the Comforter, the Holy Ghost, as was said—yet the arrangement of articles in the Faith, if religiously understood, disproves the error of Sabellius also. Return we therefore in our discourse to the point which now presses and is profitable to you.
Source: Catechetical Lectures (New Advent)