In the post on Q, the first point listed in defense of the independence of Matthew and Luke was that, otherwise, Luke would have frequently ignored Matthew’s editorial changes to Mark. In John Kloppenborg’s critical review article (“On Dispensing with Q? Goodacre on the Relation of Luke to Matthew” NTS 49 : 210-236), he lists Matthew 3:14-15, 12:5-7, 13:14-17, 14:28-31, 16:16-19, 19:9, 19b, and 27:19, 24 as passages that Luke might have found useful had the evangelist known them on page 219. Of course, the response by Farrer proponents is that the major and minor agreements of Matthew and Luke against Mark indicate that Luke was often influenced by Matthew’s editorial changes to Mark’s text. Matthew’s other editorial changes were supposedly not “Luke pleasing.” It may help to look at a specific example used by Goodacre and Kloppenborg.
Mark 1:4 describes the purpose of John’s baptizing rite to be for the forgiveness of sins, which leads to the theological conundrum of why Jesus decided to get baptized in Mark 1:9-11. The fact that Jesus was baptized by John was a sore point for many theologians. In the fourth century, Saint Jerome cites a passage allegedly from a Jewish Gospel used by the Nazoreans in which Jesus asks what sin he has committed that he would need John’s baptism for its remission (see Against the Pelagians 3.2). Moreover, John’s followers might boast that their teacher was superior to Jesus. Indeed, the book of Acts is aware of a continuing movement devoted to the Baptizer but not to Jesus (see Acts 19:1-5). Matthew and Luke found ways to navigate around this tricky theological issue in how they edit the text of Mark, but some scholars question whether they were aware of how the other dealt with the problem.
In the text of Matthew, John protests that he is the one who should be baptized by Jesus, but Jesus silences him with the reply that it is necessary for him to undergo baptism to fulfill all righteousness (Matt 3:14-15). Mark Goodacre (Case Against Q, p. 50) points out that there is a very good reason to omit the dialogue between Jesus and the Baptist in Luke; Luke has imprisoned John before the baptism (Luke 3:20)! However, Kloppenborg retorts that Luke would not have needed the expedient of removing John from the scene had the author read Matthew’s dialogue which already neutralizes theological objections to the baptism of Jesus. What do you think: did Luke simply not know Matthew’s solution or did he know it yet prefer his own way of dealing with the issue?