Reference: Matthew 16:20
Why aren’t the disciples allowed to tell that Jesus is the Messiah?
In the verses preceding Jesus’ command to the disciples that they should not tell anyone that he is the Messiah, we see two very good reasons why they shouldn’t. In short, even if the disciples (namely Peter) are correct in their belief that Jesus is the messiah, that does not necessarily mean that they have any understanding of what that really means. Following Peter’s confession that Jesus is the Messiah, Jesus points to the fact that Peter did not come to this conclusion on his own (Matt 16:17). Rather, it was from God that Peter understood this. Without the Holy Spirit it would be impossible for the disciples to proclaim the truth about Jesus.
Thus, Jesus is basically saying, “hold off for now” but it’s only a few chapters later that Jesus is saying, “go tell the whole world”. In chapter 16 however, they’re still not ready. They still don’t have the full story about the Messiah, i.e. Jesus’ death and resurrection, and they still don’t have the Holy Spirit to sustain them in spreading that message. Peter proves this only a couple verses later when he rebukes Jesus saying that he would never be put to death or raised to life (Matt. 16:21-22). Unlike Peter and the disciples, we do have the whole story, and we do have the gift of the holy spirit, so to us Jesus does not say “don’t tell,” to us he says “tell everybody!” (Matthew 28:19-20).