Because the New Testament contains four biographies of Jesus (the four Gospels), there can be up to four parallel accounts of the events recorded about Jesus’s life. These accounts will contain similarities, but also differences, to each other because each of the four Gospel authors had different intentions and purposes when composing their biographies.
An example of this is the Sermon on the Mount, as recounted in Matthew 5-7. There is a sermon recorded in Luke 6 which bears clear likenesses to Matthew’s Sermon on the Mount. How can we reconcile these two accounts? Michael Wilkins, in The Gospels and Acts (The Holman Apologetics Commentary on the Bible) analyzes the popular scholarly attempts to relate these two sermons.
He first notes the similarities:
[B]oth sermons come in the context of Jesus’ widespread speaking and healing ministry among the crowds (4: 23– 25; Luke 6: 17– 19); both begin with beatitudes; both give significant ethical teaching on love and judging; both emphasize the necessity of bearing fruit; both conclude with the parable of the wise builder.
But there also differences:
Matthew does not include the ‘woes’ of Luke’s beatitudes (Luke 6: 24– 26); Luke does not include the majority of the antitheses found in Matthew (5: 21– 48); Luke’s version of the ‘Lord’s prayer’ does not occur in his sermon but elsewhere (Luke 11: 1– 4); Luke 6: 17 puts the setting in a ‘level place,’ whereas Matthew describes a ‘mountain’ setting (5: 1).
Wilkins then examines three hypotheses about how the two sermons are related:
First, the similarities lead some to assert that Matthew and Luke present two distinct summaries of the same sermon (e.g., Bock 1994, 553; Carson 2010, 154; Osborne 2010, 160– 61).
Second, the differences lead others to suggest that Matthew and Luke record two different sermons, which Jesus gave on separate occasions but included similar content (e.g., Blomberg 1992, 96; Morris 1992, 93). Any good preacher will repeat effective illustrations and preaching points, a fact that lends support to this view.
Third, still others propose that either Matthew or Luke (or both) gathered together teachings that Jesus gave on separate occasions and presented them as if they were given in one sermon (e.g., Betz 1995, 44– 45; France 2008, 154– 155; Guelich 1982, 35; Hagner 1993, 69). The latter is usually suggested because there are parallels to Matthew’s sermon scattered throughout Luke’s Gospel (e.g., cf. 5: 13 in Luke 14: 34– 35; 5: 14 in Luke 11: 33, etc.; see Hagner 1993, 83, for a complete listing).
Wilkins’ take on these three hypotheses follows:
Since Matthew and Luke both imply that their sermons were given on one occasion, the third view is least likely. The first view is strengthened by observing the same general context, the general order, and the similar geographical setting (a mountainous area can feature flat spots) of both sermons. The second view is strengthened by recalling that Jesus went about teaching and preaching all through the countryside of Galilee for nearly two years, and he almost certainly repeated much of the same content on numerous occasions. Since nothing of great importance relies on the solution to this question, it may be best to say that until further insight is gained either the first or second view is preferable.
We don’t conclusively know how the two sermons are related, but we have some good ideas. As Wilkins says, the first and second views are preferable, but we need more evidence to decide between them.