The disciples wanted to know which of them would be the greatest in Christ's kingdom (Matthew 18:1).  Jesus did not answer the question immediately but asked a child to be with Him as He addressed the men.  It would have been a humiliating experience for them to be told that they could not enter God’s kingdom unless they changed their attitudes to become like the small child.  Although they had been chosen to be disciples and apostles, refusal to change their hearts would prevent them from entering His kingdom.
 
One of the disciples failed that critical test.  Judas Iscariot thought more of himself than of Jesus: he allowed himself to be invaded by Satan (Luke 22:3) and was excluded from God's kingdom (John 17:12).  The others did change, and they became the leaders of the Early Church.  But at this time, their hearts were proud and not humble: which was why they needed to be taught a lesson.  Pride is found in those who want to have status and exercise power. But humility is found in people who know that, compared to God, they are weak, ignorant and powerless.
 
The child who Jesus called was totally dependent on adults for everything.  There was no sense in pretending to be big when they knew they were little.  So Jesus told the disciples that if they were to be leaders in His church, they must abandon the habits of a lifetime and humble themselves.  Peter eventually learned (1 Peter 5:6), in the same way that God had commanded Solomon (2 Chronicles 7:14).  Such a person would be of the greatest use to the Lord in building His church.
 
True child-like humility is precious to God and essential in the church.  But pride and false humility disqualify people from leadership.  Those who delight in religious status are seen in sharp contrast to a child.  Child-like humility is willing for Father God to lead and provide; such people are willing to obey.  So that part of us which loves to be first (3 John 1:9) must learn that only Jesus is first; and those who are willing to let Him lead will be qualified to be leaders of others.