Would you please elaborate on what it means to be "converted and become like children" as stated in Matthew 18:1-4?
"At that time the disciples came to Jesus, saying, "Who then is greatest in the kingdom of heaven?" Then Jesus called a little child to Him, set him in the midst of them, and said, "Assuredly, I say to you, unless you are converted and become as little children, you will by no means enter the kingdom of heaven. Therefore whoever humbles himself as this little child is the greatest in the kingdom of heaven" (Matthew 18:1-4).
As you read through the Gospels, one of the notable problems the disciples struggled with was the idea of humility. They knew that they were following the Messiah and they thought much about the positions of power they would be able to wield in the Messiah's kingdom. In this particular event, they even came to Jesus to ask who he would chose to be the greatest in his kingdom.
As often happens, Jesus turned their thoughts completely upside down. He told them they would not even be able to enter the kingdom unless they could change and gain the humility exhibited by a small child. Children tend to be humble. After all, grownups are so much bigger, stronger, and knowledgeable than they are. It is a repeated theme in the New Testament. "Let nothing be done through selfish ambition or conceit, but in lowliness of mind let each esteem others better than himself" (Philippians 2:3).
On another occasion, Jesus made a similar point. "Then a dispute arose among them as to which of them would be greatest. And Jesus, perceiving the thought of their heart, took a little child and set him by Him, and said to them, "Whoever receives this little child in My name receives Me; and whoever receives Me receives Him who sent Me. For he who is least among you all will be great."" (Luke 9:46-48).
The argument about position in the kingdom continued all the way to the night of Jesus' betrayal. This is what led Jesus to put on a towel and wash his disciples feet -- a task usually reserved for the lowest slave. "Now there was also a dispute among them, as to which of them should be considered the greatest. And He said to them, "The kings of the Gentiles exercise lordship over them, and those who exercise authority over them are called 'benefactors.' But not so among you; on the contrary, he who is greatest among you, let him be as the younger, and he who governs as he who serves. For who is greater, he who sits at the table, or he who serves? Is it not he who sits at the table? Yet I am among you as the One who serves" (Luke 22:24-27).
The world encourages people to seek after themselves and their own position. But among Christians, position means nothing. Our duty is to serve others so that Christ's kingdom can be spread.