The Sermon on the Mount is not a sermon.
One of the most well-known passages in the New Testament, The Sermon on the Mount, is not a sermon. Jesus speaks to four disciples, Peter, Andrew, James, and John, while a crowd of people seem to be listening in (Matthew 5:1). The painting accompanying this post is a little misleading in this regard. In any case, both the content of the sermon and especially the ending reveal that it is intended for all who hear (Matthew 7:28-29). Jesus often pretends that his teachings are restricted to disciples, which makes little sense, especially since they are not the sharpest knives in the drawer (Mark 4:10-12).
It would be a good idea to read Matthew’s version, chapters 5-7. Luke has a condensed version, sometimes called the Sermon on the Plain (6:17-49). I’m going to stick to Matthew. Remember that the Sermon contains both the beatitudes (blessings) as well as the Lord’s Prayer. Some people think it is the clearest and most concise statement of Christianity, so much so that it could stand alone.
It’s important to remember that Jesus is not a Christian talking to other Christians. He is a Jew talking to other Jews. Christianity wouldn’t be around for another thirty years. One thing this means is that the Sermon on the Mount is not Jesus talking. It’s Matthew, writing about 50 years after the death of Jesus. And Matthew has an agenda: to show that Jesus comes to fulfill Torah, not to sweep it away. Or at least this is the diplomatic message of Matthew. What he actually says is different.