And the second time he denied with an oath. It deserves attention, that Peter, after finding that he could not escape by a simple denial, doubles his crime by adding an oath; and a little after, when he is still more vehemently pressed, he proceeds even to cursing. Hence we infer that a sinner, after having once fallen, is always hurried on from bad to worse; so that those who begin with ordinary offenses afterwards rush headlong into the basest crimes, from which at first they would have recoiled with horror. And this is the just vengeance of God, after we have deprived ourselves of the assistance of the Holy Spirit, to allow Satan a violent exercise of power over us, that, having subdued and made us his slaves, he may drive us wherever he pleases. But this happens chiefly in a denial of the faith; for when a man, through fear of the cross, has turned aside from a pure profession of the gospel, if he perceive that his enemies are not yet satisfied, will proceed farther, and what he had not ventured fully to acknowledge he denies flatly with an oath, and without any ambiguity of words. We ought also to observe, that almost in a single moment Peter thrice gave way; for this shows how unsteady we are, and how liable to fall, whenever Satan drives us. Certainly we shall never cease to fall, if the Lord do not stretch out his hand to uphold us. When the rigor of the grace of Christ was extinguished in Peter, whoever might afterwards meet hit and interrogate him about Christ, he would have been ready to deny a hundred or a thousand times. Although, then, it was very base in him to fall thrice, yet the Lord spared him by restraining the tongues of enemies from making additional attacks upon him. Thus, also, it is every day necessary for the Lord to bridle Satan, lest he overwhelm us with innumerable temptations; for though he does not cease to employ many instruments in assailing us, were it not that the Lord, paying regard to our weakness, restrains the violence of his rage, we would have to contend against a prodigious amount of temptations. In this respect, therefore, we ought to praise the mercy of the Lord, who does not permit our enemy to make advances against us, almost the hundredth part of what he would desire.

And again he denied with an oath - This is a third gradation of his iniquity. He has told a lie, and he swears to support it. A liar has always some suspicion that his testimony is not credited, for he is conscious to his own falsity, and is therefore naturally led to support his assertions by oaths.

And again he denied with an oath,.... He denied a second time, that he had ever been with Jesus, or was a disciple of his; and to put it out of all doubt, and an end to all dispute about it, and further charge of this kind, as he hoped, he annexed an oath to it: he swore by the God of truth; made a solemn appeal to the omniscient God, the searcher of hearts, that he was so far from being ever with Jesus of Nazareth, or a disciple of his, that, says he,
I do not know the man: meaning not only that he had no personal knowledge of him, or acquaintance with him; but that he had never seen the man in his life, nor did he know what manner of man he was. This, as it was a downright falsehood, it was what he had no need to have said; for there were multitudes that knew Christ in this sense, who never joined with him, or became his disciples. This was so much overdoing it, that it was much it had not given them a suspicion of him. Those that would excuse Peter's sin, by supposing that he meant, that he knew Christ to be God, and did not know him as a mere man, have no foundation for such a supposition; and indeed, such an ambiguous expression, and mental reservation, is no other than dealing fallaciously. Peter knew Christ in every sense; he knew him spiritually, whom to know is life eternal: and he valued the knowledge of him above all things else: he knew him to be God, and the Son of God; he knew him as mediator, and the Saviour of lost sinners; he knew him as man, and had had personal intimacy and conversation with him of a long time, and yet now denies he knew him; and that with an oath, adding perjury to lying; and so it is, that one sin leads on to another. This instance of Peter's shows the wickedness and deceitfulness of man's heart; and what the best of men are, or would be, when left to themselves, and of God: they become like other men, even like the men of the world, whose mouths are full of cursing and bitterness.

He denied with an oath, I do not know the man. Peter's second denial. He even denied knowing him, and that, too, with an oath. He had entered upon the downward road, and each step called for a deeper one. So it is always with sin.

He denied with an oath - To which possibly he was not unaccustomed, before our Lord called him.