Sermon on the Mount vs. Sermon on the Plain
But before we examine minutely what he is saying, we need to step back to the larger context. If you have read other parts of the New Testament, this looks a lot like the Beatitudes at the beginning of the Sermon on the Mount (Matthew 5:3-12). The difference is that in Matthew you don't have the "blessings" contrasted with the "woes" that Luke records. Why is that?
Perhaps to give Bible scholars a field day. I. Howard Marshall, whose opinions I usually respect highly, notes in his Commentary on Luke, "It is generally accepted that one basic piece of tradition underlies the two Sermons and that both Evangelists (and possibly their predecessors in the transmission of the material) have expanded it and modeled it in accord with their own purposes. A greater degree of freedom has been shown by Matthew."[1]
All this shows me is that Bible scholars like Marshall probably aren't really preachers.
You'd be amazed and amused at all the energy that has been spent trying to trace how Matthew took it one way, and Luke spun it another. This is meat for doctoral candidates because it supplies endless topics for doctoral dissertations.
The truth is that Jesus was an itinerant preacher. He often spoke for several hours per day, several days a week, to crowds in one village and then on to the next, all over Galilee and the Jordan, as well as Judea. He was teaching his hearers the basic truths of the good news of the Kingdom. Do you think he ever once repeated himself? Do you think he got up early each morning to write a brand new sermon for the day's teaching? Of course not! He spoke without notes, repeating the same truths over and over again. Certainly, with different parables and illustrations, and endless variations of them. But the same basic teaching.
If you've ever been on a speaking circuit you probably have prepared several basic speeches. You get so you don't need your notes after a while. Every speech comes out pretty much as the one before it. But they vary according to events in the news, the mindset of the particular audience, or an event that occurs in the middle of the speech that you respond to and use to illustrate a point. Sermons are much the same, and often different. Over three years, the disciples had heard the same sermons, with variations, many, many times.
So the differences we see between accounts in the four Gospels shouldn't surprise us. There was variation in the form of the basic teaching. We should expect that.
So we shouldn't be all worked up that in Luke we find both "blessings" and "woes," but in Matthew only "blessings." Instead of concentrating on the differences between the two, we do better studying Jesus' particular points recorded accurately in Luke's Gospel and learn from their particular flavor on this occasion. I, for one, see no reason that we have to conflate the Sermon on the Mount with the Sermon on the Plain. Let them be separate! Jesus could easily have uttered them both...."