the observation that in many passages Matthew and Luke repeat with only minor changes what Mark says, yet in other passages they do not follow Mark, or include stories or sayings that Mark does not have, yet match each other very closely. Many commentators, from the earliest years of Christianity, have tried to understand the relationship among the Synoptic Gospels. According to the most widely-held theory, Matthew and Luke relied on Mark and on another document (now lost) that contained mostly sayings of Jesus; this second document is referred to as “Q” from the German word “Quelle” (source). In addition, Matthew and Luke each had their own sources. Seeinterpretation.