It is a light thing for the sun to go down Namely, in an instant: for that motion of the sun is natural as to the kind of it, though miraculous for the swiftness of it; but the motion backward would be both ways miraculous.
Related Commentaries of 2 Kings 20:10
2 Kings 20:10
10 And Hezekiah answered, It is a light thing for the shadow to go down ten degrees: nay, but let the shadow return backward ten degrees.