ca. 70 A.D., Didache or Teaching of the Twelve Apostles
— Baptize in the name of the Trinity —
Now about baptism: this is how to baptize. Give public instruction on all these points, and then baptize in running water, "in the name of the Father and of the Son and of the Holy Spirit" (Matt. 28:19) (7:1).
— ca. 100 A.D., Death of Saint John, the last of the Apostles —
ca. 107 A.D., Saint Ignatius, Bishop of Antioch and disciple of the Apostle John, Letter to the Romans
— Divinity of Christ —
Address I wish [you] an unalloyed joy in Jesus Christ, our God.
ca. 125 A.D., Aristides of Athens, Apology
— Trinity; divinity of Christ —
15 [Christians] acknowledge God, the Creator and Maker of all things, in the only-begotten Son and in the Holy Spirit. Other than Him, no god do they worship.
ca. 150 A.D., Saint Justin the Martyr, First Apology
— Trinity; divinity of Christ —
13 We will prove that we worship Him reasonably; for we have learned that He is the Son of the true God Himself, that He holds a second place, and the Spirit of prophecy a third. For this they accuse us of madness, saying that we attribute to a crucified man a place second to the unchangeable and eternal God, the Creator of all things: but they are ignorant of the mystery which lies therein. …
63 They who assert that the Son is the Father are proved to know neither the Father, nor that the Father of all has a Son, who is both the first-born Word of God and is God.
ca. 181 A.D., Saint Theophilus, Bishop of Antioch, To Autolycus
— Trinity —
2:3 It is the attribute of God—of the Most High and Almighty and of the living God—not only to be everywhere, but also to hear all and to see all; for He can in no way be contained in a place. …
2:10 God, therefore, having His own Word internally in His very organs, begot Him, emitting Him along with His own Wisdom [i.e., the Holy Spirit], before all things. He had this Word for a Helper in the things which He made, and through Him were all things created. He is called Beginning, because He rules and has dominion over everything which was fashioned by Him.
He then, being Spirit of God and Beginning and Wisdom and Power of the Most High descended upon the prophets and through them spoke of the creation of the world and of all the rest; for the prophets did not exist when the world came to be, but there was Wisdom, which was in Him and which was of God, and His Holy Word, who is eternally present to Him. ...
— First extant use of the word "Trinity" in reference to the Godhead —
2:15 The three days before the luminaries were created are types of the Trinity: God, his Word, and his Wisdom.
ca. 185 A.D., Saint Irenaeus, Bishop of Lyons and disciple of Saint Polycarp, Against Heresies
— Trinity; divinity of Christ —
1:10:1 For the Church, although dispersed throughout the whole world even to the ends of the earth, has received from the Apostles and from their disciples the faith in one God, the Father Almighty, the Creator of heaven and earth … and in one Jesus Christ, the Son of God, who became flesh for our salvation; and in the Holy Spirit, who announced through the prophets the dispensations and the comings, and the birth from a Virgin, and the passion, and the resurrection from the dead, and the bodily ascension into heaven of the beloved Christ Jesus our Lord, and His coming from heaven in the glory of the Father to re-establish all things (Eph. 1:10); and the raising up again of all flesh of all humanity, in order that to Jesus Christ our Lord and God and Savior and King, in accord with the approval of the invisible Father, every knee shall bend of those in heaven and on earth and under the earth, and that every tongue shall confess Him (Phil. 2:10-11) … .
4:20:1 It was not angels, therefore, who made us nor who formed us, neither did angels have the power to make an image of God. It was not some power existing far from the Father of the universe, nor was it anyone else, other than the Word of the Lord. God had no need of others to make what He had already determined of Himself to make, as if He had not His own hands. For with Him always are the Word and the Wisdom, the Son and the Spirit, through whom and in whom He made all things freely and spontaneously; and to whom He spoke, saying: “Let us make man in our image and likeness” (Gen. 1:26). …
5:18:2 And thus it is shown that there is one God the Father, who is above all and through all and in all. The Father indeed is above all, and He is the Head of Christ. But the Word is through all, and He is the Head of the Church. The Spirit, however, is in us all, and He is the Living Water (John 7:38-39) which the Lord grants to those who rightly believe in Him and love Him and who know that there is one Father, who is above all and through all and in us all (Eph. 4:6).
ca. 200 A.D., Tertullian, The Demurrer Against the Heretics
— Trinity —
13:2 There is one only God, and none other besides Him, the Creator of the world who brought forth all things out of nothing through His Word, first of all sent forth. …
— Filioque —
13:4-5 Thenceforth He preached a new law and a new promise of the kingdom of heaven; worked miracles; was crucified, rose again on the third day; and having ascended into heaven, sat at the right of the Father; sent the Holy Spirit with vicarious power to lead those who believe.
ca. 214 A.D., Tertullian, Against Praxeas
— Trinity; divinity of Christ —
2:1 We do indeed believe that there is only one God, but we believe that under this dispensation, or, as we say, oìkonomía, there is also a Son of this one only God, His Word, who proceeded from Him and through whom all things were made and without whom nothing was made (John 1:3). … We believe He was sent down by the Father, in accord with His own promise, the Holy Spirit, the Paraclete, the Sanctifier of the faith of those who believe in the Father and the Son, and in the Holy Spirit.
2:2 That this rule of faith has been current since the beginning of the Gospel, before even the earlier heretics … .
2:4 And at the same time the mystery of the oìkonomía is safeguarded, for the Unity is distributed in a Trinity. Placed in order, the Three are the Father, Son, and Spirit. They are Three, however, not in condition, but in degree; not in substance, but in form; not in power; but in kind; of one substance, however, and one condition and one power, because He is one God of whom degrees and forms and kinds are taken into account in the name of the Father, and of the Son, and of the Holy Spirit. …
9:1 Keep always in mind the rule of faith which I profess and by which I bear witness that the Father and the Son and the Spirit are inseparable from each other, and then you will understand what is meant by it. Observe, now, that I say the Father is other, the Son is other, and the Spirit is other. This statement is wrongly understood by every uneducated or perversely disposed individual, as if it meant diversity and implied by that diversity a separation of Father, Son, and Holy Spirit. …
25:1 Thus the connection of the Father in the Son, and of the Son in the Paraclete, produces three who, though coherent, are distinct one from another. These Three are one, and yet not one: for “I and the Father are One” (John 10:30) was said in regard to their unity of substance, but not in regard to a singularity of number.
ca. 215 A.D., Saint Hippolytus of Rome, Bishop of Pontus, disciple of Irenaeus, The Apostolic Tradition
— Trinity —
4 [The newly ordained bishop shall say:] “We give you thanks, O God, through your beloved Son Jesus Christ, whom in these last days you have sent to us as Savior and Redeemer and as the angel of your will; He that is your inseparable Word, through whom you made all things, and who is well-pleasing to you; whom you sent from heaven into the womb of a Virgin, and who, dwelling within her, was made flesh and was manifested as your Son, born of the Holy Spirit and of the Virgin … .
“Gather as one in the fullness of the Holy Spirit your saints who participate; and confirm their faith in truth so that we may praise and glorify you through your Son Jesus Christ, through whom be glory and honor to you, to the Father and the Son with the Holy Spirit, in your holy Church, both now and through the ages of ages. Amen."
ca. 225 A.D., Origen, disciple of Clement of Alexandria, The Fundamental Doctrines
— Trinity; divinity of Christ —
4:4:1 For we do not hold that which the heretics imagine: that some part of the substance of God was converted into the Son, or that the Son was procreated by the Father from non-existent substances, that is, from a substance outside Himself, so that there were a time when He [the Son] did not exist. No, rejecting every suggestion of corporality, we hold that the Word and Wisdom was begotten out of the invisible and incorporeal God, without anything corporal being acted upon … . The expression which we employ, however,—that there was never a time when He did not exist,—is to be taken with a certain allowance.
For these very words when and never are terms of temporal significance, while whatever is said of the Father, Son, and the Holy Spirit, is to be understood as transcending all time, all ages, and all eternity. For it is the Trinity alone which exceeds every sense in which not only temporal but even eternal may be understood. It is all other things, indeed, which are outside the Trinity, which are to be measured by time and ages.
252 A.D., Pope Saint Cornelius, twenty-first Bishop of Rome, Letter to Cyprian of Carthage
— Trinity —
[Certain men, having fallen into a schism and now seeking reconciliation, besought Cornelius, saying:] “We are not ignorant of the fact that there is one God, and one Christ the Lord whom we confess, and one Holy Spirit; and that there must be one bishop in the Catholic Church.” (Cyprian, Letters 49 [46]:2)
ca. 255 A.D., Saint Cyprian, Bishop of Carthage, Letter to Jubaianus, A Bishop in Mauretania
— Trinity; divinity of Christ —
73:12 [If a heretic] were made a temple of God — now I ask you: of what God? Of the Creator? But that is not possible, because he does not believe in Him. Of Christ? One who denies that Christ is God cannot become His temple. Of the Holy Spirit? Since the Three are One, how were it possible for the Holy Spirit to be reconciled to him that is an enemy of either the Son or of the Father?