"He opened His mouth and began to teach them, saying…"
Notice that the people were his disciples and not the multitudes that had been following Him. He could have been a huge-crowd guy, but instead He kept going for depth. He kept saying the strong thing to thin out the crowd. In this address He lays out his kingdom program of love and humility. This was not the winning philosophy many were hoping for from the promised Messiah.
When Jesus speaks it is often surprising and always profound. He does not teach to entertain, although people could listen to Him tell stories. He spoke to communicate. And the people who heard Him understood what he was saying unless He was purposefully being opaque.
Think about the significance of this verse. The second person of the Godhead sat down, opened his mouth, and communicated in a human language with real people. He told them and us what life was supposed to be like -- how we are supposed to act. This didn't come in a dream or by an angel that was only heard by one person and then vanished. God opened His mouth and communicated in our language. He used our kind of words and syntax. What he said was written down and passed on to us.
He sat down and opened his mouth. How many millions of people have demanded that God come down to earth and do exactly what Jesus did here. He laid out how life was supposed to work. God answered the questions that we have all had.
How do we live the blessed life?
Why do you bother with sinful, obstinate, immature, inconsistent believers?
What is the problem with negative emotions?
How do I deal with temptation?
Should I make a big deal about my religious practices?
What is the deal with money, wealth, and power?
What should I do when I see people messing up all around me?
This sermon is God's answer to all these hardball questions. God was going to propositionally speak the answers to humanity’s questions. Amazing, absolutely incredible!