He has made influential contributions to research on Paul's Letter to the Galatians, the Sermon on the Mount and the Greco-Roman context of Early Christianity.
He explains that "the epitome is a composition carefully designed out of sayings of Jesus which are grouped according to thematic points of doctrine considered of primary importance.
Given that he is part of the school of thought that the answer to the Synoptic Problem lies within the Two-Source Hypothesis,[3] any discussion about the SM invariably requires some mention of the Sermon on the Plain and Q.
[1]: 17 By the 19th century, scholars widely agreed with John Calvin’s view of the Sermons as two versions of the same speech, both of which were redactional compositions and as such the direction of the scholarship turned toward seeking the sources that were used by the evangelists.
Among the hypotheses postulated during this time, Betz particularly seems to find the determinations made by Johann Gottfried Eichhorn at the turn of the century to be particularly important.
Carl Friedrich Georg Heinrici takes the work of Eichhorn further when at the turn of the 20th century he analyzed the sayings of the SM and the SP and determined their structure, composition and function.
In doing so, he concluded that the oral transmission of the sayings of Jesus was carried on by his disciples for the purpose of collecting and preserving his legacy and that the move toward written sources occurred at the same time.
He stated that each of these Sermons should be treated as independent texts as the SM is close to Jewish Palestine where Jesus originated and the SP addresses the Gentiles.
"[4]: 24 Betz feels that the work of Heinrici has been unduly overlooked by scholarship given that he offers an important perspective on the transmission of the message of Jesus and how we ended up with two speeches which are very similar and yet very different at the same time.