According to the Two Source Hypothesis accepted by a majority of contemporary scholars, the authors of Matthew and Luke each made use of two different sources: the Gospel of Mark and a non-extant second source termed Q.
In other parts of the Q material, the verbal agreement between Matthew and Luke amounts to virtual verbal identity in Greek (Luke 3:7-9; 11:9-10 and pars.).
In these instances the measure of verbal agreement seems to demand a common Greek source.
But if Mark had known Q, his criteria for selecting the material he used, and especially the sayings he omitted, cannot be explained.
The reasons given remain hypothetical (Mark as supplement to the sayings source, Q as supplement to Mark, a critical debate by Mark with the Christology of the sayings source), and fail to make plausible the considerable differences in the literary configuration and theological orientation between Q and Mark.
The Sayings Source presumably originated in (north) Palestine, since its theological perspective is directed primarily to Israel.