I am working on the post, “Other Jesus sayings,” which quite possibly may not appear until December; and learning some things I never would have supposed.
The phrase “weeping and gnashing of teeth” comes up at Matthew 8:12, Matthew 13:42, Matthew 13:50, Matthew 24:51, Matthew 25:30, Luke 13:28. So, it appears to be a particular favorite of Matthew.
The phrase “you of little faith” comes up at Matthew 6:20, 8:26, 14:31, 16:8 and 17:20, and Luke 12:28. So, it appears five times in Matthew, only once in Luke, and not at all in Mark. Thus this also appears to be a favorite of Matthew.
This suggests to what extent each Gospel author was telling his own story.