John Chrysostom, on 1Cor 15:3

"For I delivered unto you first of all that which I also received."

Neither here doth he say, "I said unto you," nor, "I taught you," but uses the same expression again, saying, "I delivered unto you that which also I received:" nor again here doth he say, "I was taught," but, "I received:" establishing these two things; first, that one ought to introduce nothing from one's self; next, that by demonstration from his deeds they were fully persuaded, not by bare words: and by degrees while he is rendering his argument credible, he refers the whole to Christ, and signifies that nothing was of man in these doctrines.

But what is this, "For I delivered unto you first of all?" for that is his word. "In the beginning, not now." And thus saying he brings the time for a witness, and that it were the greatest disgrace for those who had so long time been persuaded now to change their minds: and not this only, but also that the doctrine is necessary. Wherefore also it was "delivered" among "the first," and from the beginning straightway. And what didst thou so deliver? tell me. But this he doth not say straightway, but first, "I received." And what didst thou receive? "That Christ died for our sins." He said not immediately that there is a resurrection of our bodies, yet this very thing in truth he doth establish, but afar off and by other topics saying that "Christ died," and laying before a kind of strong base and irrefragable foundation of the doctrine concerning the resurrection. For neither did he simply say that "Christ died;" although even this were sufficient to declare the resurrection, but with an addition, "Christ died for our sins."

But first it is worth while to hear what those who are infected with the Manichaean doctrines say here, who are both enemies to the truth and war against their own salvation. What then do these allege? By death here, they say, Paul means nothing else than our being in sin; and by resurrection, our being delivered from our sins. Seest thou how nothing is weaker than error? And how it is taken by its own wings, and needs not the warfare from without, but by itself it is pierced through? Consider, for instance, these men, how they too have pierced themselves through by their own statements. Since if this be death, and Christ did not take a body, as ye suppose, and yet died, He was in sin according to you. For I indeed say that He took unto Himself a body and His death, I say, was that of the flesh; but thou denying this, wilt be compelled to affirm the other. But if He was in sin, how saith He, "Which of you convinceth Me of sin?" and "The prince of this world cometh, and hath nothing in me?" and again, "Thus it becometh Us to fulfill all righteousness?" Nay, how did He at all die for sinners, if Himself were in sin? For he who dies for sinners ought himself to be without sin. Since if he himself also sin, how shall he die for other sinners? But if for others' sins He died, He died being without sin: and if being without sin He died, He died not the death of sin; for how could He being without sin? but the death of the body. Wherefore also Paul did not simply say, "He died," but added, "for our sins:" both forcing these heretics against their will to the confession of His bodily death, and signifying also by this that before death He was without sin: for he that dies for others' sins, it followeth must himself be without sin.

Neither was he content with this, but added, "according to the Scriptures:" hereby both again making his argument credible, and intimating what kind of death he was speaking of: since it is the death of the body which the Scriptures everywhere proclaim. For, "they pierced My hands and My feet," saith He, and, "they shall look on Him Whom they pierced." And many other instances, too numerous to name all one by one, one may see in them stored up, setting forth His slaughter in the flesh and that He was slain for our sins. For, "for the sins of my people," saith one, "is He come to death:" and, "the Lord delivered Him up for our sins:" and, "He was wounded for our transgressions." But if thou dost not endure the Old Testament, hear John crying out and declaring both, as well His slaughter in the body as the cause of it: thus, "Behold," saith he, "the Lamb of God, Who taketh away the sin of the world:" and Paul saying, "For Him Who knew no sin, He made to be sin on our behalf, that we might become the righteousness of God in Him:" and again, "Christ redeemed us from the curse of the law, having become a curse for us:" and again, "having put off from himself principalities and powers, He made a show of them openly, triumphing over them;" and ten thousand other sayings to show what happened at His death in the body, and because of our sins. Yea, and Christ Himself saith, "for your sakes I sanctify Myself" and, "now the prince of this world hath been condemned;" showing that having no sin he was slain.