Servant girl accuses Peter of being Jesus' disciple.“You aren’t one of this man’s disciples too, are you?” she asked Peter.  He replied, “I am not.” It was cold, and the servants and officials stood around a fire they had made to keep warm. Peter also was standing with them, warming himself.

John 18:17,18

In John Chapter 18 we read about Jesus’ trial and Peter’s denial of Christ.  The slide into sin often follows a threefold pattern and Peter followed that pattern in classic fashion.  Psalms 1:1 details the process:

How blessed is the man who does not walk in the counsel of the wicked,
            Nor stand in the path of sinners,
            Nor sit in the seat of scoffers!

Presented as the way a righteous man does not walk, the first step downward is to "walk in the counsel of the ungodly".  In other words, don’t hang out with sinners.  Here we see Peter, simply because he was cold and needed to get warm, hanging out with the very enemies who had arrested Jesus.  The fire he sat around was built by the Temple police who had tied up Jesus’ hands with a rope, drug him into this courtyard and then spent the rest of that evening abusing Him.  Peter was snared by his desire for comfort!  The second step of the spiral into sin is to "stand in the path of sinners".  Imagine a man walking along a road who suddenly finds himself in the company of men who are clearly unsavory characters.  What does he do?  Well he passes himself off as just one of the crowd, of course.  He pretends he's one of them.  So Peter pretended he was one of the crowd, declaring, "I do not know him!"  Step three is to "sit in the seat of the scoffer (mocker)".  Imagine the scene:  The guards are busy beating Jesus and making fun of him.  From time to time one of them leaves the group around Jesus and comes over to the fire to warm himself, standing next to Peter.  Peter, forced into playing a game of intrigue, finds it necessary (as he sees it for his own safety because any of these men would have gladly run a sword through his gut) to once again deny Christ and any connection to Him.  And so it is that we see Peter joining the ranks of those who hate Christ, becoming one of them, or, as it says in Psalms 1, "sitting in the seat of the scoffer" warming himself next to their fire.

There is one redeeming factor here.  Peter, after the rooster crowed and Jesus turned and looked at him, went out and wept in repentance. He repented just like David did after his sin with Bathsheba.  Repentance is the only way to deal with sin.  The word "repent" means to stop, turn around and take a path that leads in a different direction.  Peter repented, turned away from his denial and later found himself restored to friendship with Jesus.