We are told in Mark 1:40-45 about a man with leprosy who came to Jesus, desiring to be healed. The man kneeled before Jesus and said he knew Jesus could heal him if He desired to do so. Jesus was moved with compassion and healed the man. Then, Jesus told the man not to tell anyone Jesus had healed him. He was only to go to the priest, demonstrate his cleansing and give the appropriate sacrifice. However, the man went and told everyone he could what Jesus had done.
We read the account and wonder why if the man had faith in Jesus that he did not obey Him. Jesus told him not to tell, and yet, the leper told everyone as he went. We can understand his excitement about being healed, but he should have obeyed Jesus. There are many who read the account and say they would have obeyed Jesus. They say they would have kept the secret, just as Jesus desired.
Yet, there are many who are just as guilty as the leper. Many have been told to teach and to tell people about Jesus. Our Lord wants us to go into all the world and convert as many as we can (Mark 16:15-16). We have been told to tell, and yet, very few do tell. Many claim they have faith in Jesus, but few demonstrate it by obeying Him. They are just as guilty as the leper who was told not to tell.
Read your Bible. Study it. Learn what God wants you to do, and then, do it. If any of this is hard to understand, ask an adult to help you.