"So in everything, do to others what you would have them do to you, for this sums up the Law and the Prophets."
The "Q Source" is a hypothetical document in Biblical scholarship which many scholars believe was used extensively by the authors of the Gospel of Matthew and the Gospel of Luke in the composition of their own gospels. Though there are no known copies of the Q Source in existence, the majority of scholars consider the Q Source hypothesis to be the best explanation for the composition of the synoptic Gospels.
It is thought that the Gospel of Mark, which was written first, was used as a primary document for the Gospels of Matthew and Luke. However, based on an analysis of the text, Matthew and Luke also seem to have had another source in common other than Mark. Q was first hypothesized in the early 1800's, as this mystery source would explain why the two gospels share similar stories and sometimes even similar wording.
Based on the fact that the wording is often the same, scholars argue that the Q Source must have been a written document, not simply an oral tradition in the early Church. The Q Source is thought to have been a collection of some of the sayings of Jesus, and it was probably composed in Greek. Though both Matthew and Luke seem to have used almost all of its contents, Luke appears to stick closer to the original wording of this hypothetical document than Matthew does.
The Q Source is believed to have been the source of many of the encouraging spiritual verses and notable stories from the two gospels. For example, it likely contained the Beatitudes, the Parable of the Wedding at Cana, the Parable of the Talents, the Lord's Prayer, and the Parable of the Lost Sheep. The Golden Rule, which is perhaps one of the most inspiring Biblical quotes for many Christians and which is found in both Matthew and Luke, likely originated in the Q source as well. Consider how similarly it is presented in the two gospels:
- "Do to others as you would have them do to you." (Luke 6:31)
- "So in everything, do to others what you would have them do to you, for this sums up the Law and the Prophets." (Matthew 7:12)
Some people wonder how such an important document of Jesus' sayings could have been lost. However, the truth is that early Christianity, prior to the formation of an official cannon, had a vast and diverse collection of texts. After Biblical canons began forming, many of these texts simply stopped being copied and were subsequently lost. It is not unthinkable that one of these texts, the Q Source, was what was being referred to by the author of the Gospel of Luke when he mentioned that he had investigated written sources about Jesus.
Unless a copy of the Q Source is found, we will probably never know for absolute certain if it really existed. But, as it stands, the Q Source hypothesis fits nicely with what is currently known about the composition of the gospels. It also helps to reassure believers that Jesus' words were written down and preserved very early on.