The belief that God's Kingdom will expand through advertising its immediate benefits has more to do with the spirit of this age than the Bible.  Jesus had just healed a leper (Mark 1:40-42).  Promotional policies learned from the world would demand maximum publicity from such an amazing miracle.  But the consequence of such advertisement would have been to see Jesus as a healer rather than as a Saviour.  Healing was a temporary sign that He was the promised eternal Saviour (Matthew 11:1-6).  All the bodies of those He healed or even raised from the dead, all died.  But Jesus had come to give a new life which nobody understood.  That is why He prioritised teaching the people, at the same time instructing the trainee apostles about the kingdom of heaven (Matthew 10:7).   

So, Jesus passionately warned the healed man against telling anybody.  Instead, Jesus told him to get his healing certified by the priest and then offer sacrifices, as Moses had said (Leviticus 14:1-32).  It should also have been a message to the priests that Jesus had the power of God to conquer disease.  However, what happened may be very understandable, but it was very disobedient.  The leper did not go to the priest but told everybody that he had received healing.  Many others thought that they could get similar benefits from Jesus and joined the crowd to see what He would do next.  But most of the crowd went away when they disagreed with His teaching about God's kingdom (John 6:66).

Jesus could no longer preach in the cities or towns, or even the villages.  Instead, like John the Baptist, Jesus went to the desert, hillsides and open country (Mark 10:1).  The crowds still came, but the primary agenda was teaching (Mark 6:34).  It was to be the hallmark of the apostles' ministry too (Acts 26:17-18).  The truth about God's kingdom cannot be fabricated by enthusiastic religionists: it must be revealed by God and then taught: there is no other way.  True disciples are more than consumers of religious experiences.  Jesus had said, "If you hold to my teaching, you are really my disciples. Then you will know the truth, and the truth will set you free." (John 8:31-32)

Jesus does not look for popularity but obedience.  The enthusiasm that comes from a miracle may evaporate when the next prayer is not answered as expected.  Faith trusts in the Master rather than the miracle, and continues to trust even when we see no future, because we know Jesus is the light at the end of the tunnel.  We rightly encourage believers to tell of their life with Jesus Christ.  Often an amazing answer to prayer is an encouragement to saints and sometimes curious sinners will search for the Lord.  But lasting faith does not come from believing in miracles (John 6:26) - faith comes from hearing and believing the Word of God (Romans 10:17).  Today, our job is to explain who Jesus is, and testify that we have submitted to the authority of His call. These facts are true irrespective of how God should choose to answer our prayers.  Strangely, it is our 'ordinary' submission and obedience to Christ that is the stuff of which the Kingdom is made: a consistent and transformed life is the evidence which convinces seekers.