69 Now Peter was sitting outside in the courtyard. And a servant girl came up to him and said, “You also were with Jesus the Galilean.” 70 But he denied it before them all, saying, “I do not know what you mean.” 71 And when he went out to the entrance, another servant girl saw him, and she said to the bystanders, “This man was with Jesus of Nazareth.” 72 And again he denied it with an oath: “I do not know the man.” 73 After a little while the bystanders came up and said to Peter, “Certainly you too are one of them, for your accent betrays you.” 74 Then he began to invoke a curse on himself and to swear, “I do not know the man.” And immediately the cock crowed. 75 And Peter remembered the saying of Jesus, “Before the cock crows, you will deny me three times.” And he went out and wept bitterly.
When we look back on Peter's rash boast, 'I will never deny Thee, Lord' it becomes clear that here was a man who did not know his own heart, did not know that there was that in him, as in all of us, that would not only deny Christ but also, Judas-wise, betray Him. And especially in a crisis of this magnitude, when ultimate issues of good and evil were let loose in the world, he did not stand a chance. But more. His words, 'I do not know the man' were truer than he knew, for he did not know Jesus in the only way that can keep a man from failing in the evil day (cf Psalm 9:10; Daniel 11:32; Philippians 3:10). To know Christ in this necessary way is to know His cross, and Peter had never come to this point. And every Christian who denies his Lord, saying thereby, 'I do not know the man' is also proclaiming something unmistakable about his own experience - that he is a stranger to the cross or has forsaken the place to which Christ has called him. Indeed, every sin we commit proclaims openly that we do not know Him (cf 1 John 2:4; 3:6). When we commit sin it means that for that particular moment we have chosen to part company with Christ and find Him an embarrassment to us. The practical value of this disastrous experience for Peter was that it brought him to an end of himself. It was in that place of abject failure and collapse that he learned the truth about himself at last, and that the foundations of the new Peter, the rock, the man of the cross (cf 1 Peter) were laid. His faith, such as it was, was purged and purified and reborn, as it were, and emerged a new thing.