Seems to me there's three parts ...
"Unless you change"
"Become like children"
"Enter the kingdom of heaven"
... of Matthew 18:3, the scripture I'm preaching about this Sunday. But it also seems to me that there is a whole boatload to say about each of those three parts. Like it could be a series of three sermons.
So I'm going with that middle part this week - "Become like children." In response to the disciples' question, "Who is the greatest in the kingdom of heaven," Jesus tells them that they're not even going to GET IN if they don't become like children. And as for being the "greatest"? Forget about it.
I read in a couple commentaries this week that in the time of Jesus, a child was most definitely not in a position of earthly greatness. Children were not valued intrinsically, they were considered property, they had neither power nor control. And yet in order to enter the kingdom of heaven, according to Jesus, this is the position that we must assume.
Now some people think "become like children" means be all innocent and pure. (Obviously these are people who do not have much experience with real live children.) I don't think so. That just wouldn't follow from the literary context. That interpretation doesn't make sense in response to the disciples' provoking question.
To yield all power and control of your life, to confess your utter dependence upon God, to become like children in not conforming to earthly definitions of power and success - these are the characteristics I believe Jesus was referring to in this passage. That matches up with other places where Jesus is teaching about the "greatest." The greatest is the least, the servant of all, the humble one.
I'm preparing this sermon in the middle of Vacation Bible School week, with 250 kids running all over the building. There has been all of the energy, excitement, and barely controlled chaos that usually accompanies VBS, and I am loving it. I have been reminded numerous times that I am not really in control of things!
I feel like when I am talking with the kids, I am definitely entering the kingdom of heaven.