The disciples ask Jesus, "Who is the greatest in the kingdom of heaven?" Thinking that He was about to set up a great temporal kingdom, they want to know who would hold the primary offices and posts of honor and profit. Mark informs us that they had disputed this subject while traveling (Mark 9:34). Jesus asks them what they had been arguing about. Luke adds that Jesus perceives their thoughts (Luke 9:47). The disciples, conscious that Jesus is aware of their dispute, are at first embarrassed into silence, but they eventually ask Him to decide it for them. Jesus' reply are the parables found in Matthew 18:2-14.
Martin G. Collins
Parables of the Millstone and the Lost Sheep
Suppose we were asked, "Who are the greatest people in your town?" What would we turn to as qualities that exemplify greatness? Would it be money, prestige, learning, or military conquest? Just before this incident, the disciples were arguing about which of them would be greatest among them (Mark 9:33-37). Jesus responds to the disciple's question by using a child.
He is not saying that heaven is populated by little children. He means that a child's attitudes of easy dependence, trust, unpretentiousness, awareness of weakness, lack of knowledge, and submission to parents illustrate what we as converted adults must become toward God. Jesus is not saying every child is like His illustration; He is using one to illustrate an ideal. It is essential that we grasp that we must turn, change, to become like the ideal.
John W. Ritenbaugh
Fully Accepting God's Sovereignty, Part Three: The Fruits