2 Chronicles 32:1-3

1 After these things and this loyalty, Sennacherib king of Assyria came, invaded Judah, and encamped against the fortified cities, thinking to take them.

2 When Hezekiah saw that Sennacherib had come and intended to fight against Jerusalem,

3 He decided with his officers and his mighty men to stop up the waters of the fountains which were outside the city [by enclosing them with masonry and concealing them], and they helped him.