II Chronicles 32:2-5

And when Hezekiah saw that Sennacherib had come, and that his purpose was to make war against Jerusalem, he consulted with his leaders and commanders to stop the water from the springs which were outside the city; and they helped him. Thus many people gathered together who stopped all the springs and the brook that ran through the land, saying, “Why should the kings of Assyria come and find much water?” And he strengthened himself, built up all the wall that was broken, raised it up to the towers, and built another wall outside; also he repaired the Millo in the City of David, and made weapons and shields in abundance.