Peradventure there shall lack five of the fifty righteous: wilt thou destroy all the city for lack of five? Literally, on account of five, i.e. because they are wanting. A rare example of holy ingenuity in prayer.
Abraham, instead of pleading for the city's safety on account of forty-five, deprecates its destruction on account of five. And its said, If I find there forty and five, I will not destroy it.