According to John Welch, it has been suggested that certain portions of the Sermon on the Mount are Anti-Pauline and were purposely added during the time of Paul. The most likely deprecation of Paul in the Sermon on the Mount is the passage that condemns anyone who teaches people to ignore even the least of the commandments in the law of Moses -- he will be called "the least in the kingdom of heaven" (Matthew 5:19) Paul is the obvious figure in early Christianity who taught and promoted the idea that Christians need not observe the law of Moses, and his ideas met considerable hostility among both Jews and certain Christians. Since Paul was known as "the least" of the apostles (1 Corinthians 15:9), it seems quite plausible that early Christians would have seen in Matthew 5:19 a direct criticism of Paul's position, if not of Paul himself. Thus, the absence from the Sermon at the Temple of the chief bits of evidence of an anti-Pauline hand in the Sermon on the Mount supports the Book of Mormon. [John W. Welch, The Sermon at the Temple and the Sermon on the Mount, F.A.R.M.S., pp. 108-110]
“Think Not That I Am Come to Destroy the Law or the Prophets”
In the midst of his Sermon at the Temple, and just preceeding some comments on ancient matters of law, Jesus says the following:
Think not that I am come to destroy the law or the prophets. I am not come to destroy but to fulfil;
For verily I say unto you, one jot nor one tittle hath not passed away from the law, but in me it hath all been fulfilled.
According to John Welch, the Ten Commandments have recently been analyzed by Moshe Weinfeld at Hebrew University in Jerusalem as also temple related materials--presenting the requirements that a person must satisfy before approaching the temple in Jerusalem. I don't know if you know this, but as you went up toward the temple in Jerusalem there were ancient warnings saying, "Caution, you are approaching sacred territory. Do not come any closer if you are not pure." They would list the Ten Commandments or things like that so that people would know that these are the requirements. If you are not complying with them, you had better not come into this sacred place. There are also some Greek temples that have similar kinds of inscriptions on the foundation stones that require a person coming into the temple to be pure--not just through some kind of ritual, but also pure in conduct and in their heart. [John W. Welch, "The Beatitudes--Christ's Teachings," in Teachings of the Book of Mormon, Semester 4, p. 137]