What does Mark 1:45 mean?After Jesus heals the man with leprosy, He tells the man to show himself to the priests, to complete the process outlined in Leviticus 13—14. This would provide a witness to the priests and show that Jesus had not come to replace Judaism, but to fulfill it. Instead, the man talks freely about his healing without giving or, perhaps, understanding the context. Even more troublesome, Jesus' fame as a miracle healer spreads further. If the man had obeyed Jesus' instructions, the Jewish religious leaders might have had a better chance at understanding Jesus as the Messiah.
The man healed of leprosy doesn't understand the significance of Jesus' command, so he doesn't follow it. There's no way to know what spiritual damage he caused, but it had a direct influence on Jesus' ministry. For the time being, Jesus can't enter a town, stay at a friend's house, or go to the synagogue. He has no problem going to lonely, desolate places to pray and spend time with God the Father, but now He lives in the wilderness, with His growing crowd. Instead of defining the context of His ministry, He's forced to work with what He has. As a result, He accumulates crowds that can only be fed by miracle (Matthew 14:15; 15:33) and has no place to lay His head (Matthew 8:20).
The process of discipleship, finding a church, being taught, and being recognized as a Christian is an important one. Young believers tend to have great enthusiasm, but if they aren't grounded in God's Word, their account of what Jesus has done for them may be wrong or incomplete. The exuberance and lack of context in the man's reaction to God's blessing is the same type that can lead to such false teachings as the Prosperity Gospel.
Even though Jesus heals the man and makes him ceremonially clean, the man still has free will, and he uses it. We do the same thing when we think we know best and ignore God's commands. God can redeem any situation that comes about because of our disobedience. And yet, that doesn't mean the outcome will be as good as it could have been. The initial failure of Israel to enter the Promised Land is a classic example: God redeemed the situation, but the nation suffered forty years of loss and wandering before finally achieving their goal. Very often, we don't know the reasons for the rules given in the Bible. But we should trust the One who gave them enough to follow anyway.