i. e. “Whosoever will smite the Jebusites, let him reach both the lame and the blind, who are the hated of David’s soul, by the gutter or water-course, and he shall be chief.” The only access to the citadel was where the water had worn a channel (some understand a subterranean channel), and where there was, in consequence, some vegetation in the rock. Joab (see the marginal reference) took the hint, and with all the activity that had distinguished his brother Anabel 2 Samuel 2:18, climbed up first. The blind and the lame are either literally such, placed there in derision by the Jebusites who thought the stronghold impregnable, or they are the Jebusite garrison, so called in derision by David.
Wherefore they said ... - i. e. it became a proverb (as in 1 Samuel 19:24). The proverb seems merely to have arisen from the blind and the lame being the hated of David’s soul, and hence, to have been used proverbially of any that were hated, or unwelcome, or disagreeable.