XIII. To sum up my discourse:— Glorify Him with the Cherubim, who unite the Three Holies into One Lord, and so far indicate the Primal Substance as their wings open to the diligent. With David be enlightened, who said to the Light, In Your Light shall we see Light, that is, in the Spirit we shall see the Son; and what can be of further reaching ray? With John thunder, sounding forth nothing that is low or earthly concerning God, but what is high and heavenly, Who is in the beginning, and is with God, and is God the Word, and true God of the true Father, and not a good fellow-servant honoured only with the title of Son; and the Other Comforter (other, that is, from the Speaker, Who was the Word of God). And when you read, I and the Father are One, keep before your eyes the Unity of Substance; but when you see, “We will come to him, and make Our abode with him,” remember the distinction of Persons; and when you see the Names, Father, Son, and Holy Ghost, think of the Three Personalities.
XIV. With Luke be inspired as you study the Acts of the Apostles. Why do you range yourself with Ananias and Sapphira, those vain embezzlers (if indeed the theft of one's own property be a vain thing) and that by appropriating, not silver nor any other cheap and worthless thing, like a wedge of gold, or a didrachma, as did of old a rapacious soldier; but stealing the Godhead Itself, and lying, not to men but to God, as you have heard. What? Will you not reverence even the authority of the Spirit Who breathes upon whom, and when, and as He wills? He comes upon Cornelius and his companions before Baptism, to others after Baptism, by the hands of the Apostles; so that from both sides, both from the fact that He comes in the guise of a Master and not of a Servant, and from the fact of His being sought to make perfect, the Godhead of the Spirit is testified.
XV. Speak of God with Paul, who was caught up to the third Heaven, and who sometimes counts up the Three Persons, and that in varied order, not keeping the same order, but reckoning one and the same Person now first, now second, now third; and for what purpose? Why, to show the equality of the Nature. And sometimes he mentions Three, sometimes Two or One, became That which is not mentioned is included. And sometimes he attributes the operation of God to the Spirit, as in no respect different from Him, and sometimes instead of the Spirit he brings in Christ; and at times he separates the Persons saying, “One God, of whom are all things, and we in Him; and one Lord Jesus Christ, by whom are all things, and we by Him;” at other times he brings together the one Godhead, “For of Him and through Him and in Him are all things;” that is, through the Holy Ghost, as is shown by many places in Scripture. To Him be glory for ever and ever. Amen.
Source: Orations (New Advent)