M-source, which is sometimes referred to as M document, or simply M, comes from the M in "Matthean material". It is a hypothetical textual source for the Gospel of Matthew. M-source is defined as that special material of the Gospel of Matthew that is neither Q-source or Mark and is thought by some to be the Gospel of the Hebrews.
Nineteenth century New Testament scholars who rejected the traditional perspective of the priority of Matthew in favor of Marcan priority speculated that the authors of Matthew and Luke drew the material they have in common with the Gospel of Mark from that Gospel. Matthew and Luke, however, also share large sections of text which are not found in Mark. They suggested that neither Gospel drew upon the other, but upon second common source, termed the Q.
This two-source hypothesis, speculates that Matthew borrowed from both Mark and a hypothetical sayings collection, called Q. For most scholars, the Q collection accounts for what Matthew and Luke share — sometimes in exactly the same words — but are not found in Mark. Examples of such material are the Devil's three temptations of Jesus, the Beatitudes, the Lord's Prayer and many individual sayings.
In The Four Gospels: A Study of Origins (1924), Burnett Hillman Streeter argued that a third source, referred to as M and also hypothetical, lies behind the material in Matthew that has no parallel in Mark or Luke. This Four Source Hypothesis posits that there were at least four sources to the Gospel of Matthew and the Gospel of Luke: the Gospel of Mark, and three lost sources: Q, M, and L. (M material is represented by green in the above chart.)
Throughout the remainder of the 20th century, there were various challenges and refinements of Streeter's hypothesis. For example, in his 1953 book The Gospel Before Mark, Pierson Parker posited an early version of Matthew (Aram. M or proto-Matthew) as the primary source.
In the study of biblical literature, some scholars believe that an unknown redactor composed M, a Greek-language proto-Gospel. It may have been in circulation (in written form) from about the time of the composition of the Synoptic Gospels (i.e. between 65 and ad 95).
Synoptic Gospels and the Nature of M 
The relationship among the three synoptic gospels goes beyond mere similarity in viewpoint. The gospels often recount the same stories, usually in the same order, sometimes using the same words. Scholars note that the similarities between Mark, Matthew, and Luke are too great to be accounted for by mere coincidence. If the four-source hypothesis is correct, then M would probably have been a written document and contained the following:
- Parable of the weeds among the wheat
- Parable of the treasure
- Parable of the pearl
- Parable of the net
- Parable of the unforgiving servant
- Parable of the labourers in the vineyard
- Parable of the two sons
- Parable of the ten virgins
Primary Gospels 
The primary gospels are those original gospels upon which all others are based. Those who support the Four Document Hypothesis believe these to be the Gospel of Mark, Q and M.
The Gospel of Mark (40–70) 
Eusebius, in his catalog of ancient church writings, puts the Gospel of Mark in his Homologoumena or “accepted” category. Both modern and ancient Biblical scholars agree that it was the earliest Canonical account of the life of Jesus Christ. It is a primitive, primary source, incorporated into both the Canonical Matthean Gospel as well as Luke-Acts.
Scholars agree that the Gospel of Mark was not written by any of the Apostles, but by some insignificant figure in the early church. Notwithstanding its shortcomings, it was probably included in the Canon because the Early Church Fathers believed it was a reliable account of the life of Jesus of Nazareth.
Eusebius, in his Church History records that the writer of this gospel was a man named Mark who was Peter’s interpreter. It was believed that his accounts of Jesus were historically accurate, but that there was some chronological distortion. It is further agreed that this gospel was originally composed in Koine Greek, near Rome.
Q source (40–70) 
Q source is a hypothetical textual source for the Gospel of Matthew and Gospel of Luke. It is defined as the "common" material found in Matthew and Luke but not in Mark. This ancient text supposedly contained the logia or quotations from Jesus. Scholars believe that an unknown redactor composed Greek-language proto-Gospel. The name Q, coined by the German theologian and biblical scholar Johannes Weiss.
M source (30–50) 
The third primary source is M. Although most scholars accept the Four Document Hypothesis, many are not entirely happy with it. The difficulty tends to center around M. The Four Document Hypothesis explains the triple tradition by postulating the existence of a lost "Matthean" document known as M. It is this, rather than Marcan priority, which forms the distinctive feature of the Four Document Hypothesis as against rival theories.
While the Four Document Hypothesis remains a popular explanation for the origins of the synoptic gospels, the question is how could a major and respected source, used in a canonical gospel, totally disappear? Why was M never mentioned in any of the Church catalogs? Also not one scholar from the time of Christ to Jerome has ever mentioned it. Until these issues are resolved, M will remain in doubt.
See also 
Online translations of the Gospel of Matthew:
- A FOUR DOCUMENT HYPOTHESIS
- Net Bible
- Early Christian Writings
- The Development of the Canon of the New Testament
- D. R. W. Wood, New Bible Dictionary, Inter Varsity Press, 1996 p. 739.
- Bart Erhman, Jesus: Apocalyptic Prophet of the New Millennium, Oxford University Press, p.80-81
- Streeter, Burnett H. The Four Gospels. A Study of Origins Treating the Manuscript Tradition, Sources, Authorship, & Dates. London: MacMillian and Co., Ltd., 1924.
- Pierson Parker. The Gospel Before Mark. Chicago: University of Chicago Press, 1953.
- William R. Farmer, The Synoptic Problem: a Critical Analysis, Macmillan, 1981 p. 196
- Everett Falconer Harrison, Introduction to the New Testament, Wm. Eerdmans 1971 p. 152.
- Ehrman, Bart D. (2004). The New Testament: A Historical Introduction to the Early Christian Writings. New York: Oxford. p. 84. ISBN 0-19-515462-2.
- Robert E. Van Voorst, Jesus outside the New Testament: an introduction to the ancient evidence studying the historical Jesus, Wm. B. Eerdmans Publishing, 2000 p. 143
- Daniel J. Scholz, Jesus in the Gospels and Acts: Introducing the New Testament, Saint Mary's Press, 2009 p. 90
- James R. Edwards, The Hebrew Gospel and the Development of the Synoptic Tradition, Wm. B. Eerdmans Publishing, 2009 p. 228
- Raymond E. Brown, Introduction to the New Testament, New York: Anchor Bible, 1997 pp. 164 - 167.
- Christoph Heil & Jozef Verheyden (Ed.) The Sayings Gospel Q: collected essays, Vol. 189 of Bibliotheca Ephemeridum theologicarum Lovaniensium, Peeters Publishers Pub., 2005 pp. 163 - 164
- Jones, Brice (2011). Matthean and Lukan Special Material: A Brief Introduction with Texts in Greek and English. Wipf and Stock Publishers. ISBN 978-1-61097-737-1.
- Martin Hengel, The Four Gospels and the One Gospel of Jesus Christ Trinity Press, SCM 2000 p.207- 210
- Delbert Royce Burkett, Rethinking the Gospel Sources, Vol. 2, Society of Biblical Lit, 2009 p. 135 - 141
- A FOUR DOCUMENT HYPOTHESIS