Oral gospel traditions called the M source for Matthew and the L source for Luke, which may have been a mix of written and oral material (see Two-source hypothesis). Most scholars believe that the author of John's gospel used oral and written sources different from those available to the Synoptic authors – a "signs" source, a "revelatory discourse" source, and others – although there are indications that a later editor of this gospel may have used Mark and Luke. Oral transmission may also be seen as a different approach to understanding the Synoptic Gospels in New Testament scholarship. Current theories attempt to link
Law and Gospel (Cranach) them with serpents; they need only look upon the serpent placed on a cross by Moses to be saved. Luther considered the story an example of faith and illustrative of Gospel. The mixture of Old and New Testament concerns in both halves of the panels illustrates that Gospel is not only found in the New Testament. For Luther and Cranach, artworks such as "Law and Gospel" were intended to instill understanding of scripture and Lutheran thought, and the images were deemed acceptable so long as they were subordinate to the written word. The role of these Reformation "Merkbilder" contrasted with