The statement "unless you change and become like little children, you will never enter the kingdom of heaven" comes from Matthew 18:3 and is also found in Mark 10:15 and Luke 18:17. Jesus made this statement to His disciples, teaching them that to enter the kingdom of God, one must have the humility, simplicity and trust of a child.

Jesus is warning against ambition, especially the kind of pride and desire for status or greatness that His disciples were displaying at the time. In Matthew 18:1-4, the disciples had been arguing about who would be the greatest in the kingdom of heaven, and Jesus used the example of a child to teach them that humility and a child-like attitude are necessary for entering the kingdom.