Matthew 16:20

Then charged he his disciples
When Peter had so freely and fully confessed him to be the Messiah, and which was the sense of all the disciples; and when Christ had expressed his approbation of his confession, and had promised such great and excellent things upon it, he gave a strict charge unto his disciples,

that they should tell no man that he was Jesus the Christ.
The word Jesus is not in some copies; and is left out in the Syriac, Arabic, and Persic versions; nor does it seem absolutely necessary; it was enough to charge them to tell no man that he was the Messiah: his reasons for it might be, lest his enemies, the Scribes and Pharisees, should be the more provoked and incensed against him, and seek his death before his time; and lest the jealousy of the Romans should be stirred up, who might fear he would set up himself against Caesar, as king of the Jews, which might lead them to take measures obstructive of his further designs; and lest some persons, hearing of this, should rise and proclaim him king of the Jews, who were big with the notion of the Messiah being a temporal prince: and moreover, because the disciples were to attest the truth of this after his resurrection; and he chose, for the present, that the people should collect this from his own ministry and miracles, which were sufficient to lead them into the knowledge of it, without any declarations of their's: and though they were possessed of true faith in him, as such, for themselves, as yet they had not the gifts and abilities to defend those doctrines respecting his person, and his offices, they had after the Spirit was poured down upon them.