numerous times in the Gospel of Mark Jesus tells a follower who correctly 'guesses' that he is the Christ to maintain secrecy, "commanded him to tell no one". a few examples:
Mark 3:11-12
And whenever the unclean spirits saw him, they fell down before him and cried out, “You are the Son of God.” 12 And he strictly ordered them not to make him known.Mark 4:33-34 33
With many such parables he spoke the word to them, as they were able to hear it. 34 He did not speak to them without a parable, but privately to his own disciples he explained everything.Mark 8:29-30
29 And he asked them, “But who do you say that I am?” Peter answered him, “You are the Christ.” 30 And he strictly charged them to tell no one about him.there are more examples.
http://users.ox.ac.uk/~sben0056/essays/messianicsecret.htmthoughts on why Jesus felt the need to hide aspects of the nature of his mission from the outside world?