This is one of my favorite chapters in all the Bible. Watching Jesus move through these unusual pastoral experiences back-t0-back makes me love and admire him all the more. I love how the disciples are all trying to keep up with and understand him.
The passive voice in the verb "be one flesh" is interesting. It is something done to the couple, they are made to be one flesh. The beginning in Genesis is the standard for marriage and divorce.
Unless you come to the kingdom as a child, you can't come. I illustrated this for Layne, who was sitting on my lap, by talking about her falling into the deep end of the pool. She won't get out unless she calls for and accepts help, like a little child.
The disciples marvel, more than once, at how hard it is to be saved.