Charles Spurgeon Commentary 2 Kings 20:1

"In those days was Hezekiah sick unto death. And Isaiah the prophet the son of Amoz came to him, and said unto him, Thus saith Jehovah, Set thy house in order: for thou shalt die, and not live." — 2 Kings 20:1 (ASV)

That is to say, in the common course of providence, without a miracle, Hezekiah must have died. God did by no means change when afterwards He permitted him to live. This time He spoke after the order of nature; the next time He spoke according to the extraordinary work of His marvelous power.