In historical-critical analysis, the L source is an inferred oral tradition which Luke used when composing his gospel. It includes the virgin birth of Jesus and many of Jesus' best loved parables. Like Matthew's unique source, known as M, the L source has important parables. Two which appear in L are the Good Samaritan and the Prodigal Son. I. Howard Marshall states "Luke rightly regarded these sources as reliable".
According to the Four Document Hypothesis, Luke combined Mark, the Q source, and L to produce his gospel. The material in L, like that in M, probably comes from the oral tradition. Luke's special material composes nearly half of his gospel.
The question of how to explain the similarities among the Gospels Matthew, Mark, and Luke is known as the synoptic problem. The hypothetical L source fits a contemporary solution in which Mark was the first gospel and Q was a written source for both Matthew and Luke.
- Funk, Robert W., Roy W. Hoover, and the Jesus Seminar. The five gospels. HarperSanFrancisco. 1993. "Introduction," p 1-30.
- 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.
- IVP New Testament Commentary 21st century edition pp 979
- Theissen, Gerd and Annette Merz. The historical Jesus: a comprehensive guide. Fortress Press. 1998. translated from German (1996 edition). Chapter 2. Christian sources about Jesus.