When God gave Hezekiah more years to live, he also promised to protect Jerusalem. When Hezekiah responded to Sennacherib’s later invasion (2 Kings 19:14–19) by asking Isaiah for advice (2 Kings 19:2), he was following a well-known example.
for My sake and for … David: God reminded Hezekiah of this promise during Sennacherib’s invasion (2 Kings 19:34).