David said on that day, “Whoever strikes the Jebusites, let him get up to the water shaft and strike the lame and the blind who are hated by David’s soul.” Therefore they say, “The blind and the lame cannot come into the house.” Bible

“water shaft.” The Jebusite city was built on the south end of Mount Zion and its main water source was the Gihon Spring, a spring on the south-east end of the city, just outside the city wall. The Jebusites had a shaft leading down from their city to the spring, and Joab used that shaft to gain access to the city and conquer it.

Commentary for: 2 Samuel 5:8