continued from here.
The traditions of Jesus as we have them thus do not focus on hell, but clearly indicate that he believed it existed and that many would end up there. Of course we might debate the potential difference between what Jesus said historically and the way the gospel writers present him, but in this particular case such debates will likely end up in speculation rather than clear certainty. The comments on hell in the Jesus tradition go deep.
For example, there are the statements we mentioned earlier in the chapter about those among the living who will be thrown directly into Gehenna from the earth (Mark 9:47; Matt. 10:28). These two statements fit some of the criteria that the most skeptical historians have used to try to distinguish between things Jesus said and things they do not think he said. Here, these two sayings come from what most experts would consider two different layers of Jesus tradition, two separate sources of material. Mark is one source. Then Matthew 10:28 and Luke 12:4 represent some other, different source. 
Matthew and Luke have other material about hell in common. The queen of the south and the Ninevites who repented will rise from the dead at the judgment and condemn Jesus' generation for not repenting and believing (Matt. 12:41-42; Luke 11:31-32). Things will go better for ancient Tyre, Sidon, and Sodom in the judgment than for Bethsaida, Chorazin, and Capernaum, which largely did not accept Jesus (Matt. 11:20-24; Luke 10:13-14). They all will rise for the final verdict. Interestingly, there seem to be levels of punishment.
Matthew in particular repeats numerous times the imagery of "weeping and gnashing of teeth" for the condemned, often taking place after being cast out into "outer darkness" (Matt. 8:12; 13:42, 50; 22:13; 24:51; 25:30). In one place, we hear that this is an eternal punishment (Matt. 25:46; cf. 18:8), that the wicked are going to a place that was originally prepared for the Devil and his angels (25:41). The other gospels do not mention that hell is a place where the wicked go forever...
 This other source is sometimes called "Q," which is short for the German word for source, "Quelle." However, it is not important for us here that Q be a real document. Clearly Matthew got this saying from some source other than Mark, because the saying is not in Mark.