Let him not go down (mh katabatw). Second aorist active imperative of katabainw with mh in a prohibition in the third person singular. The usual idiom here would be mh and the aorist subjunctive. See Mark 13:15 ; Matthew 24:17 when these words occur in the great eschatological discussion concerning flight before the destruction of Jerusalem. Here the application is "absolute indifference to all worldly interests as the attitude of readiness for the Son of Man" (Plummer).