2 Chronicles 32:2-5

When Hezekiah saw that Sennacherib had come and that he intended to wage war against Jerusalem, he consulted with his officials and military staff about blocking off the water from the springs outside the city, and they helped him. They gathered a large group of people who blocked all the springs and the stream that flowed through the land. “Why should the kings of Assyria come and find plenty of water?” they said. Then he worked hard repairing all the broken sections of the wall and building towers on it. He built another wall outside that one and reinforced the terraces of the City of David. He also made large numbers of weapons and shields.