II Chronicles 32, 33
Now in chapter 32, we find that,
Sennacherib, the king of Assyria was coming against them, he entered into Judah, and he encamped against the fenced cities, he thought to win them for himself. And when Hezekiah saw that Sennacherib was come, and that he was purposed to fight against Jerusalem, he took counsel with the princes and with his mighty men to stop the waters of the fountains which were without the city: and they did help him (2Ch 32:1-3).
Now he said, "Why should he come and find all of this water here? Let's stop up all of the springs and all so that they won't know where the water supplies are that are outside of the city of Jerusalem." So they went about and they stopped up all of the springs on the outside of the city of Jerusalem.
And they set the captains of war over the people, they gathered them together in the street of the gate of the city, and spake to them, saying, Be strong and courageous, be not afraid nor dismayed for the king…