Matthew 26:35

But you will ask, whether it were possible that Peter should not have been offended, when once the Saviour had said, All ye shall be offended in me. To which one will answer, what is foretold by Jesus must of necessity come to pass; and another will say, that He who at the prayer of Ninevites turned away the wrath He had denounced by Jonas, might also have averted Peter's offence at his entreaty. But his presumptuous confidence, prompted by zeal indeed but not a cautious zeal, became the cause not only of offence but of a thrice repeated denial. And since He confirmed it with the sanction of an oath, some one will say that it was not possible that he should not have denied Him. For Christ would have spoken falsely when he said, Verily I say unto thee, if Peter's assertion, I will not deny thee, had been true. It seems to me that the other disciples having in view not that which was first said, All ye shall be offended, but that which was said to Peter, Verily I say unto thee, &c. made a like promise with Peter because they were not comprehended in the prophecy of denial. Peter said unto him, Though I should die with thee, yet will I not deny thee. Likewise also said all the disciples. Here again Peter knows not what he says; he could not die with Him who was to die for all mankind, who were all in sin, and had need of some one to die for them, not that they should die for others.

What the One affirms by His power of foreknowledge, the other denies through love; whence we may take a practical lesson, that in proportion as we are confident of the warmth of our faith, we should be in fear of the weakness of our flesh. Peter seems culpable, first, because he contradicted the Lord's words; secondly, because he set himself before the rest; and thirdly, because he attributed every thing to himself as though he had power to persevere strenuously. His fall then was permitted to heal this in him; not that he was driven to deny, but left to himself, and so convinced of the frailty of his human nature.

"But Peter answered and said, Though all men should be offended because of Thee, yet will I never be offended." What sayest thou, O Peter? the prophet said, "The sheep shall be scattered;" Christ hath confirmed the saying, and sayest thou, No? Is not what passed before enough, when Thou saidst, "Far be it from Thee," and thy mouth was stopped? For this then He suffers him to fall, teaching him thereby to believe Christ in all things, and to account His declaration more trustworthy than one's own conscience. And the rest too reaped no small benefit from his denial, having come to know man's weakness, and God's truth. For when He foretells anything, we must no longer be subtle, nor lift up ourselves above the common sort. For, "thy rejoicing," it is said, "thou shall have in thyself, and not in another." For where he should have prayed, and have said, Help us, that we be not cut off, he is confident in himself, and saith, "Though all men should be offended in Thee, yet will I never;" though all should undergo this, I shall not undergo it, which led him on by little and little to self-confidence. Christ then, out of a desire to put down this, permitted his denial. For since he neither submitted to Him nor the prophet (and yet for this intent He brought in the prophet besides, that they may not gainsay), but nevertheless since he submitted not to His words, he is instructed by deeds. And He said sharply reproving him, and showing that his fall was more grievous than the rest, and needed more help. For the matters of blame were two; both that he gainsaid; and, that he set himself before the other; or rather a third too, namely, that he attributed all to himself. To cure these things then, He suffered the fall to take place, and for this cause also leaves the others, and addresses Himself earnestly to him. […]

Peter said unto Him, Even if I must die with Thee, yet will I not deny Thee. Likewise also said all the disciples. Then cometh Jesus with them unto a place called Gethsemane, and saith unto the disciples, Sit ye here, while I go away …

There follows the excuse of Peter: Peter saith to him etc. Peter excuses himself: yea, though I should die with thee, I will not deny thee. And yet he was afraid, because at the voice of a maid he denied. Jerome says that he did …