Then Isaiah said, "This is the sign to you from the LORD, that the LORD will do the thing which He has spoken: shall the shadow go forward ten degrees or go backward ten degrees?"
2 Kings 20:9
Surrounding context
20:8 And Hezekiah said to Isaiah, "What is the sign that the LORD will heal me, and that I shall go up to the house of the LORD the third day?"
20:9 Then Isaiah said, "This is the sign to you from the LORD, that the LORD will do the thing which He has spoken: shall the shadow go forward ten degrees or go backward ten degrees?"
20:10 And Hezekiah answered, "It is an easy thing for the shadow to go down ten degrees; no, but let the shadow go backward ten degrees."