Matthew 16:18 And I say also unto thee, that thou art Peter, and upon this rock I will build my church; and the gates of hell shall not prevail against it.
Again, some persons erroneously believe that Peter was granted power to forgive sins, but in the first example given, we see Christ addressing all of the disciples, not only Peter. In fact, the next example speaks about Peter being given the keys of heaven, and authority to bind and loose things in heaven and earth as the case might be. Peter, as well as all of the other disciples were never to do any of these things on, or of their own.
They were commissioned to declare to the people the written word of God, which contains the terms and conditions upon which pardon may be granted, but they were not to take it upon themselves to try to pardon anyone. In fact, later on in the next verses we see where even Peter was in need of pardon.
Matthew 16:20 Then charged he his disciples that they should tell no man that he was Jesus the Christ. 21 From that time forth began Jesus to shew unto his disciples, how that he must go unto Jerusalem, and suffer many things of the elders and chief priests and scribes, and be killed, and be raised again the third day. 22 Then Peter took him, and began to rebuke him, saying, Be it far from thee, Lord: this shall not be unto thee.
Matthew 16:23 But he turned, and said unto Peter, Get thee behind me, Satan: thou art an offence unto me: for thou savourest not the things that be of God, but those that be of men.
May The Lord add His blessing to the study of His word. God bless!