Melachim Bais 20:9

9 And Yeshayah said, This Ot (Sign) shalt thou have from Hashem, that Hashem will do the thing that He hath spoken: shall the tzel (shadow) go forward eser ma’alot (ten steps), or go backward eser ma’alot?

Melachim Bais 20:9 Meaning and Commentary

And Isaiah said, this sign shalt thou have of the Lord, that the Lord will do the thing that he hath spoken,.... Cure him of his disorder, so that he should be able to go to the temple on the third day:

shall the shadow go forward ten degrees, or go back ten degrees? that is, the shadow of the sun on a dial plate; it was left to his option to choose which he would, as the confirming sign of his recovery.

Melachim Bais 20:9 In-Context

7 And Yeshayah said, Take a develet te’enim. And they took and laid it on the shechin (boil, inflamed spot) and he recovered [See Isaiah 38:21].

8 And Chizkiyahu (Hezekiah) said unto Yeshayah, What shall be the Ot (Sign) that Hashem will heal me, and that I shall go up into the Beis Hashem on the Yom HaShelishi?

9 And Yeshayah said, This Ot (Sign) shalt thou have from Hashem, that Hashem will do the thing that He hath spoken: shall the tzel (shadow) go forward eser ma’alot (ten steps), or go backward eser ma’alot?

10 And Chizkiyahu (Hezekiah) answered, It is a simple matter for the tzel to go forward eser ma’alot; no, but let the tzel return backward eser ma’alot.

11 And Yeshayah HaNavi cried out unto Hashem; and He brought the tzel (shadow) eser ma’alot backward, by which it had gone on the ma’alot Achaz (sundial of Ahaz).