Charles Ellicott Commentary 2 Kings 20:10

"And Hezekiah answered, It is a light thing for the shadow to decline ten steps: nay, but let the shadow return backward ten steps." — 2 Kings 20:10 (ASV)

It is a light thing for the shadow to go down. —Because that was the ordinary course of things. As a natural phenomenon, of course, the sudden extension of the shadow would have been as wonderful as its retrogression; but what is in any way a familiar occurrence must necessarily seem easier than what has never fallen under observation.

To go down. —Rather, to spread. The Septuagint has κλῖναι, another use of the Hebrew verb. The Targum, Syriac, and Arabic render “to go forward” (march).