Why Does Jesus Not Want Talk of His Miracles?
Why does Jesus say not to tell of his miracle in Mark 1: 43-44 but says to tell in Mark 5:18-20?
There is no definitive answer as to why in some situations Jesus instructed the healed person to tell others and in others not to tell. Context is probably the most important clue.
The most commonsense answer is practical concerns. Many times in the Gospels after Jesus performs a miracle of healing, crowds gather around him, making it nearly impossible for him to move around (Matt. 8:18, Mark 1:45).
Mark 1 tells of a leper who is cured. Jesus instructs him to not to tell anyone but to go immediately to the priests and perform the prescribed cleansing. Jesus wants the priests to be the first to hear of the miracle. This was to be proof for the priests of the legitimacy of Jesus' ministry. Perhaps Jesus did not want the man to tell anyone because Jesus did not want his enemies among the priests to have time to prepare a counterargument to the miracle. If they knew ahead of time that the man was coming, they could conspire to cast doubt on the story or its details.
In Mark 5, Jesus heals a possessed man. Jesus does not instruct the man to tell everyone but simply to go home and share the joy with his family. This is not especially surprising and seems quite straightforward.