Cyprian a.d. 200–258
Finally, when, after the resurrection, the apostles are sent by the Lord to the heathens, they are bidden to baptize the Gentiles “in the name of the Father, and of the Son, and of the Holy Ghost.” How, then, do some say, that a Gentile baptized without, outside the Church, yea, and in opposition to the Church, so that it be only in the name of Jesus Christ, everywhere, and in whatever manner, can obtain remission of sin, when Christ Himself commands the heathen to be baptized in the full and united Trinity?
Epistle LXXII.5.18
Novatian a.d. 210–280
And now, indeed, concerning the Father, and the Son, and the Holy Spirit, let it be sufficient to have briefly said thus much, and to have laid down these points concisely, without carrying them out in a lengthened argument. For they could be presented more diffusely and continued in a more expanded disputation, since the whole of the Old and New Testaments might be adduced in testimony that thus the true faith stands. But because heretics, ever struggling against the truth, are accustomed to prolong the controversy of pure tradition and Catholic faith, being offended against Christ; because He is, moreover, asserted to be God by the Scriptures also, and this is believed to be so by us; we must rightly—that every heretical calumny may be removed from our faith—contend, concerning the fact that Christ is God also, in such a way as that it may not militate against the truth of Scripture; nor yet against our faith, how there is declared to be one God by the Scriptures, and how it is held and believed by us.
A Treatise of Novatian Concerning the Trinity. Chapter XXX.
Alexander, Bishop of Alexandria a.d. 273–326
Therefore, when the holy prophets, and all, as I have said, who righteously and justly walked in the law of the Lord, together with the entire people, celebrated a typical and shadowy Passover, the Creator and Lord of every visible and invisible creature, the only-begotten Son, and the Word co-eternal with the Father and the Holy Spirit, and of the same substance with them, according to His divine nature, our Lord and God, Jesus Christ, . .
Epistles on the Arian Heresy And the Deposition of Arius. Chapter I.7
Therefore to the unbegotten Father, indeed, we ought to preserve His proper dignity, in confessing that no one is the cause of His being; but to the Son must be allotted His fitting honour, in assigning to Him, as we have said, a generation from the Father without beginning, and allotting adoration to Him, so as only piously and properly to use the words, “He was,” and “always,” and “before all worlds,” with respect to Him; by no means rejecting His Godhead, but ascribing to Him a similitude which exactly answers in every respect to the Image and Exemplar of the Father. But we must say that to the Father alone belongs the property of being unbegotten, for the Saviour Himself said, “My Father is greater than I.” And besides the pious opinion concerning the Father and the Son, we confess to one Holy Spirit, as the divine Scriptures teach us; who hath inaugurated both the holy men of the Old Testament, and the divine teachers of that which is called the New.
Epistles on the Arian Heresy And the Deposition of Arius. Chapter I.12
Augustine of Hippo a.d. 354–430
Those holy angels come to the knowledge of God not by audible words, but by the presence to their souls of immutable truth, i.e., of the only-begotten Word of God; and they know this Word Himself, and the Father, and their Holy Spirit, and that this Trinity is indivisible, and that the three persons of it are one substance, and that there are not three Gods but one God; and this they so know that it is better understood by them than we are by ourselves.
Augustine The City of God Book 11 Chapter 29
The true objects of enjoyment, then, are the Father and the Son and the Holy Spirit, who are at the same time the Trinity, one Being, supreme above all, and common to all who enjoy Him, if He is an object, and not rather the cause of all objects, or indeed even if He is the cause of all. For it is not easy to find a name that will suitably express so great excellence, unless it is better to speak in this way: The Trinity, one God, of whom are all things, through whom are all things, in whom are all things. Thus the Father and the Son and the Holy Spirit, and each of these by Himself, is God, and at the same time they are all one God; and each of them by Himself is a complete substance, and yet they are all one substance. The Father is not the Son nor the Holy Spirit; the Son is not the Father nor the Holy Spirit; the Holy Spirit is not the Father nor the Son: but the Father is only Father, the Son is only Son, and the Holy Spirit is only Holy Spirit. To all three belong the same eternity, the same unchangeableness, the same majesty, the same power. In the Father is unity, in the Son equality, in the Holy Spirit the harmony of unity and equality; and these three attributes are all one because of the Father, all equal because of the Son, and all harmonious because of the Holy Spirit.
On Christian Doctrine Book I. Chapter 5.5
Wherefore, our Lord God helping, we will undertake to render, as far as we are able, that very account which they so importunately demand: viz., that the Trinity is the one and only and true God, and also how the Father, the Son, and the Holy Spirit are rightly said, believed, understood, to be of one and the same substance or essence; in such wise that they may not fancy themselves mocked by excuses on our part, but may find by actual trial, both that the highest good is that which is discerned by the most purified minds, and that for this reason it cannot be discerned or understood by themselves, because the eye of the human mind, being weak, is dazzled in that so transcendent light, unless it be invigorated by the nourishment of the righteousness of faith.
On the Trinity Book I. Chapter 2.4
And I would make this pious and safe agreement, in the presence of our Lord God, with all who read my writings, as well in all other cases as, above all, in the case of those which inquire into the unity of the Trinity, of the Father and the Son and the Holy Spirit; because in no other subject is error more dangerous, or inquiry more laborious, or the discovery of truth more profitable.
On the Trinity Book I. Chapter 3.5
All those Catholic expounders of the divine Scriptures, both Old and New, whom I have been able to read, who have written before me concerning the Trinity, Who is God, have purposed to teach, according to the Scriptures, this doctrine, that the Father, and the Son, and the Holy Spirit intimate a divine unity of one and the same substance in an indivisible equality; and therefore that they are not three Gods, but one God: although the Father hath begotten the Son, and so He who is the Father is not the Son; and the Son is begotten by the Father, and so He who is the Son is not the Father; and the Holy Spirit is neither the Father nor the Son, but only the Spirit of the Father and of the Son, Himself also co-equal with the Father and the Son, and pertaining to the unity of the Trinity. Yet not that this Trinity was born of the Virgin Mary, and crucified under Pontius Pilate, and buried, and rose again the third day, and ascended into heaven, but only the Son. Nor, again, that this Trinity descended in the form of a dove upon Jesus when He was baptized; nor that, on the day of Pentecost, after the ascension of the Lord, when “there came a sound from heaven, as of a rushing mighty wind,” the same Trinity “sat upon each of them with cloven tongues like as of fire,” but only the Holy Spirit. Nor yet that this Trinity said from heaven, “Thou art my Son,” whether when He was baptized by John, or when the three disciples were with Him in the mount, or when the voice sounded, saying, “I have both glorified it, and will glorify it again;” but that it was a word of the Father only, spoken to the Son; although the Father, and the Son, and the Holy Spirit, as they are indivisible, so work indivisibly. This is also my faith, since it is the Catholic faith.
On the Trinity Book I. Chapter 4.7
Some persons, however, find a difficulty in this faith; when they hear that the Father is God, and the Son God, and the Holy Spirit God, and yet that this Trinity is not three Gods, but one God; and they ask how they are to understand this: especially when it is said that the Trinity works indivisibly in everything that God works, and yet that a certain voice of the Father spoke, which is not the voice of the Son; and that none except the Son was born in the flesh, and suffered, and rose again, and ascended into heaven; and that none except the Holy Spirit came in the form of a dove. They wish to understand how the Trinity uttered that voice which was only of the Father; and how the same Trinity created that flesh in which the Son only was born of the Virgin; and how the very same Trinity itself wrought that form of a dove, in which the Holy Spirit only appeared. Yet, otherwise, the Trinity does not work indivisibly, but the Father does some things, the Son other things, and the Holy Spirit yet others: or else, if they do some things together, some severally, then the Trinity is not indivisible. It is a difficulty, too, to them, in what manner the Holy Spirit is in the Trinity, whom neither the Father nor the Son, nor both, have begotten, although He is the Spirit both of the Father and of the Son.
On the Trinity Book I. Chapter 5.8.
https://apostles-creed.org/confessi...theology/early-church-fathers-quotes-trinity/
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