2 Chronicles 32:3 (KJV)

After these things, and the establishment thereof, Sennacherib king of Assyria came, and entered into Judah, and encamped against the fenced cities, and 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 his princes and his mighty men to stop the waters of the fountains which were without the city: and they did help him.

So there was gathered much people together, who stopped all the fountains, and the brook that ran through the midst of the land, saying, Why should the kings of Assyria come, and find much water?

Also he strengthened himself, and built up all the wall that was broken, and raised it up to the towers, and another wall without, and repaired Millo in the city of David, and made darts and shields in abundance.