The Sermon on the Mount begins with beatitudes, and the Olivet Discourse begins with Woes.  As N. T. Wright and others have shown, the two series are similar in a number of particulars.  The connections between the two discourses continue after the beatitudes/woes section, evident in significant verbal repetition.  To wit:

“Kill”: Jesus uses the verb in 5:21  After that it comes up only in Matthew in 19:18, until we get to 23, where it describes what scribes, Pharisees, hypocrites do (23:31, 35).

“Hell” ( geenna ): Used 7x in the book, 3x in ch. 5.   It’s found in 10:28; 18:9, and then as the destination of the disciples of the Pharisees and of the Pharisees themselves (23:15, 33).

“Altar”: Found in 5:23-24; 23:18-20, 35.

“Gift”: In 5:23-24, then 3x in ch 23:18-19.

Swearing by God’s throne comes up in both 5:23 and 23:22.

The sermon lays out a righteousness that surpasses the righteousness of the scribes.  In fact, it is a righteousness that in many particulars directly opposes the “righteousness” of the scribes and Pharisees.