Many scholars look to a hypothetical Proto-Luke as the source behind the material unique to Luke but not found in Matthew and Mark.
In 1940 Pierson Parker concluded that a close connection existed between the Gospel according to the Hebrews and this hypothetical “Proto-Luke” document:
…the presence in this gospel of Lukan qualities and parallels, the absence from it of definitive… Markan elements… all point to one conclusion, viz., that the source of the Gospel according to the Hebrews… was most closely related to sources underlying the non-Markan parts of Luke, that is, Proto-Luke. (Pierson Parker; A Proto-Lukan Basis for the Gospel according to the Hebrews; Journal of Biblical Literature 59 (1940) p. 478)
However, I believe we may easily conclude that the material unique to Luke comes not from a Proto-Luke or L-Source at all, but actually from the Gospel according to the Hebrews.
To begin with Luke admits to having had source documents when writing his gospel (Luke 1:1-4) and the fact is that several of the surviving readings from the Gospel according to the Hebrews parallel Luke only and not Matthew. For example only Luke gives Yeshua’s age as being thirty (Lk. 3:23); only Luke includes the account of Yeshua being comforted by an angel (Lk. 22:43); only Luke includes the discussion about eating the Passover as described in Luke 22:45 and only Luke includes Yeshua’s words at the crucifixion “father forgive them…” (Lk. 23:34). All of these are found in the surviving Gospel according to the Hebrews fragments. There are also Lukan elements even in Gospel according to the Hebrews material that also parallels Matthew. The immersion account as cited by Epiphanius also included the words “in the form of [a dove]” (as in Luke’s account) and the phrase “I have this day begotten you” (as in Luke’s account in the Greek Western type text of Codex D).
The correlation with the Greek Western text type of Codex D is also extremely important, but I will have to visit that topic in a future blog.
If Mark is secondary and not primary, as we have found that it is, we should expect that the Synoptic source would have readings which parallel Matthew only, readings which parallel only Luke and readings which are common to Matthew and Luke (and sometimes Mark) but should not expect readings which parallel only Mark and this is exactly the case with the Gospel according to the Hebrews.
This is why restoring the original underlying Hebrew of the Gospel according to the Hebrews is such an important part of this project, because the Gospel according to the Hebrews is the original Jewish Gospel behind Matthew Mark and Luke!