In a 1987 article and a 2005 revision (published in his Studies in Matthew ), Dale Allison offers a careful treatment of the structure of the sermon on the mount.

To begin with, there are multiple verbal parallels between 4:25-5:2 and 7:28-8:1: “great crowds followed him” (4:25; 8:1); “the crowds” (5:1; 7:28); “the mountain” (5:1; 8:1); “he taught/his teaching” (5:2; 7:28). At the very least, the sermon is framed by these inclusions.

Allison also finds similarities between 5:3-12 and 7:13-27, blessings offered before His teaching and warnings appended to the end. Within the narrative inclusios, Allison matches the “nine blessings” with the “three warnings.”

5:13-16 provides an opening description of the people of Jesus in the world, and this is filled out in three large sections in 5:17-7:12. 5:17 and 7:12 both refer to the fulfillment of the “law and the prophets,” and thus form a neat inclusio around the teaching of the sermon. Within this section, Allison finds a triple sequence: Torah (5:17-48), the “Christian cult” (6:1-18), and “social relations” (6:19-7:12). These reinterpret rabbinic descriptions of the “three pillars of the world” - Torah, temple service, and acts of righteousness.

Each of these three sections is organized by triads. Allison says that the “antitheses” section in 5:17-48 is organized in two groups of triads. 5:21 and 5:33 are the only verses that use the full phrase “you have heard that the ancients were told,” and v. 33 uses palin (“again”), which Allison takes as a sign of a resumption, the beginning of a fresh section. The first triad treats murder, adultery, and divorce; the second treats swearing, retribution, and love for enemies.

6:1-18 is clearly organized as a triad. Jesus deals with the three duties of almsgiving, prayer, and fasting with very similar language. The central section is expanded with the introduction of the Lord’s prayer (which contains 2 triads of petitions), and a statement on forgiveness. Thus, the central section of the triad is a triad-with-a-triad: Don’t pray like Gentiles; the Lord’s Prayer; forgive.

Allison suggests that 6:19-7:12 returns to the double-triadic structure of 5:17-48, with added words of encouragement and assurance. The first deals with the disciple’s use of wealth: Don’t store earthly treasures; parable about eye; parable about servants. Then encouragement concerning the Father’s provision. The second sequence, beginning in 7:1, follows a similar organization: “Don’t judge”; parable about the eye; parable about pigs and pearls. Then encouragement concerning the Father’s willingness to answer prayer.

7:12 closes the main teaching section with a summary statement that echoes 5:17.

The rest is me, not Allison. This analysis suggests an overall chiastic structure for the sermon:

A. Jesus ascends mountain surrounded by crowds, 4:25-5:2.
B. Blessings, 5:3-12.
C. Fulfill law and prophets, greater righteousness, 5:13-20.
D. Two triads on Law, 5:21-48.
E. Triad on duties of piety, 6:1-18.
D’. Two triads on relations with wealth and brothers, 6:19-7:11.
C’. This is law and prophets, 7:12.
B’. Warnings, 7:13-27.
A’. Jesus descends mountain surrounded by crowds, 7:28-8:1.

By this organization, the center of the center is Jesus’ teaching on prayer, and the center of that center is the giving of the Lord’s prayer, and the center of that center appears to be the first three petitions - hallowed be Thy name, Thy kingdom come, Thy will be done on earth as it is in heaven. This is the greater righteousness - to pray for the coming of God’s kingdom in obedient honor to His name.