The three-source hypothesis is a candidate solution to the synoptic problem. It combines aspects of the two-source hypothesis and the Farrer hypothesis. It states that the Gospel of Matthew and the Gospel of Luke used the Gospel of Mark and a sayings collection as primary sources, but that the Gospel of Luke also used Gospel of Matthew as a subsidiary source. The hypothesis is named after the three documents it posits as sources, namely the sayings collection, the Gospel of Mark, and the Gospel of Matthew.
The sayings collection may be identified with Q, or some (typically narrative-related) material normally assigned to Q may instead be attributed to Luke's use of Matthew.
This theory has been advocated by Heinrich Julius Holtzmann, Eduard Simons,Hans Hinrich Wendt, Edward Y. Hincks, Robert Morgenthaler and Robert H. Gundry.