Confessions similar to this had been made previously after certain miracles were performed (e.g., Matt. 14:33; John 1:49), but they appear to be more like exclamatory guesses at the truth than the calm expression of a settled conviction.
Jesus continued in Matthew 16:18 - "And I also say to you that you are Peter, and on this rock I will build My church." The Greek words for "Peter" and "rock" are petros and petra, respectively. Although these words are similar, the differences clearly distinguish them. Petros is a masculine noun meaning "a piece of rock." Petra is a feminine noun meaning "a mass of rock." Thus, these two words are not only opposite in gender, they are as distinct as a small rock is from a slab of bedrock (cf. Matt. 7:24). Contrary to Catholic claims, the church was not built upon a "small male stone" (i.e., Peter); it was built upon a "massive female stone." Peter's confession that Jesus is the Christ, the Son of the living God, is a gigantic "rock" in the sense that this truth is the most fundamental of all truths pertaining to man's redemption--it is the bedrock! Thus, Jesus is saying that the church would be established upon the solid foundation of truth that He was the Christ, the Son of the living God.
Our Lord stated that He would build His "church," not churches. First, it should be observed that the church wasn't in existence yet at that moment (it was established on the day of Pentecost in Acts 2). Also, Jesus would not build a plurality of churches--just one (cf. Eph. 1:22,23; 4:4). No man has the right to seek the church of his own choice for there is only one church! The one that Christ died for to establish is the one in which all the saved are found (cf. Acts 2:47).
Jesus declared that "the gates of Hades shall not prevail against it." Hades is the realm where departed spirits go to wait at death until the resurrection. There are three interpretations as to what the "it" refers to here:
Although all three interpretations are Biblically true, the third one is the only feasible interpretation here grammatically. Since Jesus used the neuter "it," He certainly wasn't referring to the "church" (feminine; cf. Eph. 5:23ff) or "Himself" (masculine).
Jesus promised to give Peter the keys of the kingdom of heaven (Matt. 16:19). Certainly the "church" is "the kingdom of heaven" because Jesus would not build one thing and then give Peter the keys to something else! To give a person the keys to something is to give them the authority to both open it and admit in whom they will. Jesus is here giving Peter this authority regarding the church, although the apostles were all later promised this same right (cf. Matt. 18:18). It is easily observed that the apostles' actions (specifically Peter's) on Pentecost and with Cornelius opened up the kingdom of God to both Jews and Gentiles on the same terms (cf. Acts 2 & 10).
"And whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven." According to the Greek tenses in this verse, Jesus is saying that those things that would be bound or loosed on earth have already been bound or loosed in heaven. The apostles would lay down the laws of the new kingdom, although they would not personally originate them. They would instead learn via the Holy Spirit what had been approved or prohibited, and then they would teach those things (cf. John 14:26; 16:13-15).
"Then He commanded His disciples that they should tell no one that He was Jesus the Christ" (Matt. 16:20). This restriction wasn't lifted until after the resurrection of Jesus (cf. Matt. 28:19,20). If they had gone forth proclaiming this truth with their immature understanding of it, they would have caused more harm than good at that point in history. Additionally, the public declaration of this truth at that time would have likely accelerated the persecution against Jesus and brought Him to His death prior to the divinely appointed time.