Irenaeus — Against Heresies Against Heresies, III.18 (St. Irenaeus)

Continuation of the foregoing argument. Proofs from the writings of St. Paul, and from the words of Our Lord, that Christ and Jesus cannot be considered as distinct beings; neither can it be alleged that the Son of God became man merely in appearance, but that He did so truly and actually.

1. As it has been clearly demonstrated that the Word, who existed in the beginning with God , by whom all things were made, who was also always present with mankind , was in these last days, according to the time appointed by the Father , united to His own workmanship, inasmuch as He became a man liable to suffering, [it follows] that every objection is set aside of those who say, If our Lord was born at that time, Christ had therefore no previous existence . For I have shown that the Son of God did not then begin to exist, being with the Father from the beginning; but when He became incarnate, and was made man, He commenced afresh the long line of human beings, and furnished us, in a brief, comprehensive manner, with salvation ; so that what we had lost in Adam — namely, to be according to the image and likeness of God — that we might recover in Christ Jesus .

2. For as it was not possible that the man who had once for all been conquered, and who had been destroyed through disobedience, could reform himself, and obtain the prize of victory; and as it was also impossible that he could attain to salvation who had fallen under the power of sin — the Son effected both these things, being the Word of God , descending from the Father , becoming incarnate, stooping low, even to death, and consummating the arranged plan of our salvation , upon whom [ Paul ], exhorting us unhesitatingly to believe , again says, Who shall ascend into heaven? That is, to bring down Christ; or who shall descend into the deep? That is, to liberate Christ again from the dead. Romans 10:6-7 Then he continues, If you shall confess with your mouth the Lord Jesus , and shall believe in your heart that God has raised Him from the dead, you shall be saved. Romans 10:9 And he renders the reason why the Son of God did these things, saying, For to this end Christ both lived, and died, and revived, that He might rule over the living and the dead. Romans 14:9 And again, writing to the Corinthians, he declares, But we preach Christ Jesus crucified; 1 Corinthians 1:23 and adds, The cup of blessing which we bless, is it not the communion of the blood of Christ? 1 Corinthians 10:16

3. But who is it that has had fellowship with us in the matter of food? Whether is it he who is conceived of by them as the Christ above, who extended himself through Horos, and imparted a form to their mother; or is it He who is from the Virgin, Emmanuel , who ate butter and honey, Isaiah 8:14 of whom the prophet declared, He is also a man , and who shall know him? Jeremiah 17:9 He was likewise preached by Paul : For I delivered, he says, unto you first of all, that Christ died for our sins , according to the Scriptures ; and that He was buried, and rose again the third day, according to the Scriptures . 1 Corinthians 15:3-4 It is plain, then, that Paul knew no other Christ besides Him alone, who both suffered, and was buried, and rose gain, who was also born, and whom he speaks of as man. For after remarking, But if Christ be preached, that He rose from the dead, 1 Corinthians 15:12 he continues, rendering the reason of His incarnation , For since by man came death, by man [came] also the resurrection of the dead. And everywhere, when [referring to] the passion of our Lord, and to His human nature , and His subjection to death, he employs the name of Christ , as in that passage: Destroy not him with your meat for whom Christ died. Romans 14:15 And again: But now, in Christ , you who sometimes were far off are made near by the blood of Christ . Ephesians 2:13 And again: Christ has redeemed us from the curse of the law, being made a curse for us: for it is written, Cursed is…