Sons of the kingdom is a Semitic idiom meaning “people (here, the Jewish people) who belong to the kingdom.” In 9.15 “sons of the bride chamber” means wedding guests, and the Jews could also speak of “sons of the city,” “sons of the coming age,” and “a son of the Law.” Bibel im heutigen Deutsch, 1st edition translates sons of the kingdom by “people who actually were appointed for God’s new world.” INCL renders “people who were supposed to have been God’s people”; Malay common language version has “people who were supposed to enjoy the blessings of God’s rule”; and Barclay has “those who were born to be members of the Kingdom.” Translators will find all of these useful models.
In place of the passive for will be thrown into, some Greek manuscripts have the active form, “will go into.” TC-GNT believes that the evidence favors the passive, and most all modern translations apparently accept this reading. New English Bible translates “will be driven out” (so also New American Bible), while Jerusalem Bible renders “will be turned out.” For those languages that do not normally use a passive construction, an agent must be supplied, as in “God will throw them” or “God will have his angels throw them.”
The outer darkness is also used elsewhere by Matthew as a description of the doom that awaits people who reject God (22.13; 25.30). The figure of crying and gnashing teeth appears in conjunction with the outer darkness in 25.30 and is used without the figure of darkness in 24.51. Luke 13.28-29 is a parallel to verses 11-12, only in reverse order.
The outer darkness, obviously a reference to hell, represents what it is like where God is not found. Translators should try to retain this image, saying “the dark world where God is not (or, does not go)” or “the dark place away from God’s rule.” Some have said “the great dark place of hell.” “Dark” or “darkness” may have to be rendered as “black” or “place with no light.”
Men means people, not just males.
Gnash their teeth is a favorite Matthean formula; see 13.42, 50; 22.13; 24.51; 25.30. Elsewhere it occurs only in Luke 13.28. It means to grind or strike the teeth together in rage or pain. It may be necessary to add “in great pain” to the phrase gnash their teeth if this expression is not known.
Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .