Additional comments on structure:
Paying attention to the structure of the Sermon on the Mount can be difficult, because it isn’t linear in its argument, and doesn’t flow the way essays and speeches in Western culture do. As a result, there’s little agreement among scholars on its structure—or even if it has one. Some, like W. D. Davies, go so far as to conclude that it has none at all, but is merely “an agglomeration of sources and even of snippets of tradition.” This allows us to read it as a disjointed jumble of topics with little real coherence or unity.
I believe the Sermon has a strong structure which makes sense if we understand and remember the common literary structures of the Old Testament, and particularly its use of parallelism. Parallelism of various types is common in the literature of the ancient world, both for aesthetic effect and as an aid to memory—which was of great importance in those largely pre-literate cultures. The Old Testament is no exception. Most simply, we see parallelism in individual verses, such as the step parallelism (AB A’B’ pattern) of Isaiah 28:17:
I will make justice the measuring line,
and righteousness the plumb line.
In verses like Isaiah 41:9, we see an AB B’A’ pattern, called inverted parallelism or chiasm:
I took you from the ends of the earth,
and from its farthest corners I called you.
(The word “chiasm” comes from the Greek letter X (pronounced khi); if one draws lines between the parallel elements in these lines, they form an X.)
These basic forms can be extended beyond just two lines into more complex parallels.
This is especially true of inverted parallelism, which scholars like Kenneth Bailey argue is used to structure paragraphs, whole passages, and perhaps even entire biblical books. These larger forms are also commonly referred to as chiasms or chiastic structures; since the original visual metaphor is lost on this scale, however, I prefer the term “ring composition” for these texts. In such literary units, the parallelism serves a purpose beyond the aesthetic or the mnemonic: it also functions in part to shape and reinforce the message and meaning of the text. The climax of the piece typically comes not at the end but in the center section around which it turns. The opening and closing sections are next in importance because they set the theme of the composition and provide the context for its argument.
I believe the Sermon on the Mount is a ring composition, and that understanding this opens up the meaning of the text and helps us make sense of its more obscure parts. Viewed in this way, for instance, it isn’t necessary to say, “The connection of Matt. 7:1–11 (cf. Luke 6:37–38, 41–42) to the preceding context is not easy to discern,” or to conclude that Matthew 7:6 is a “detached unrelated saying,” as David L. Turner does, because the structure shows us the connections.