Peter finds himself under suspicion and in his eagerness to defend himself, Jesus’ prediction of his denial comes to pass.
Peter occupies an ambivalent position in the Gospel of Mark. He is one of the first disciples that Jesus calls (1:16). Along with James and John, he is allowed to witness things such as the raising of Jairus’ daughter and the The Transfiguration was a mountaintop event in which Jesus was transformed and became dazzling white, in a manner that suggested his future glory. Peter, James, and John witnessed Jesus' transfiguration; Moses and Elijah appeared on the mountain and talked with Jesus. The event, which is... More that the other disciples are excluded from. He gives a true confession of Jesus’ identity as the Christ (8:29).
On the other hand, he also misunderstands Jesus’ ministry and Jesus calls him “Satan” as a result (8:33). Most pointedly, even though all of Jesus’ disciples desert him, Peter is singled out for his unfaithfulness. Three times Peter is given the opportunity to claim Jesus as his Lord and three times Peter denies knowing him, going so far as to curse and swear. Though cursing and swearing in the modern world entails profanity, in the ancient context it probably involved an oath that invoked the name of God. Thus Peter compounds his unfaithfulness by calling on God as a witness to his lies. The crowing of a rooster serves as a supernatural reminder of Jesus’ prediction and it causes Peter to burst into tears at his own duplicity. The attention that Mark pays to Peter’s unfaithfulness is another example of the way in which Mark may be nudging his readers toward the proclamation of Paul, especially as Peter and Paul sometimes found themselves at odds over the necessity of requiring observance of Jewish law (Galatians 2).