Q source
The phrase "(there shall be) weeping and gnashing of teeth" (in the original Greek ὁ κλαυθμὸς καὶ ὁ βρυγμὸς τῶν ὀδόντων) appears seven times in the New Testament as a description on the fate of the unrighteous ones at the conclusion of the age. It is thought to derive from a logion in the hypothetical Q source, which yielded and . The other five occurrences (, , , , and ) are all within the context of parables and are widely held to be redactional additions by Matthew. (source) Others, however, believe redactional theories of the parables are speculative at best, and offer little explanation as to the meaning of this phrase, and only speculate as to why Matthew and Luke included this apparently familiar saying.