Hezekiah had asked Isaiah, "What will be the sign that the LORD will heal me and that I will go up to the temple of the LORD on the third day from now?"
Isaiah answered, "This is the LORD's sign1 to you that the LORD will do what he has promised: Shall the shadow go forward ten steps, or shall it go back ten steps?"
References for 2 Kings 20:9
"It is a simple2 matter for the shadow to go forward ten steps," said Hezekiah. "Rather, have it go back ten steps."
References for 2 Kings 20:10
Then the prophet Isaiah called upon the LORD, and the LORD made the shadow go back3 the ten steps it had gone down on the stairway of Ahaz.
References for 2 Kings 20:11