It is an interesting thing that Jesus would heal or do other things to demonstrate His deity and then tell people to tell no one. This seems odd at first reading. I think there are two important reasons why He did that. First, He wanted to be known primarily as a healer of souls, not merely as a healer of bodies. Certainly, physical healing was a part of His ministry, and it had its purpose (showed He was indeed the Messiah). However, He did not want crowds coming to Him merely seeking physical healing instead of spiritual transformation. You see clearly in our own day how people try to "use" Jesus to get what they want, rather than to submit to His Lordship. The same issues existed 2,000 years ago. Another reason why He gave such a command was due to the primary purpose for which He came. His mission was to come and die as a substitute in our place. The revelation of Jesus as the Messiah had to begin discreetly and proceed by stages so that the plan of God for the death of His Son would not be jeopardized by any excesses of popular enthusiasm. This is what is referred to as the "messianic secret."