Melachim Bais 20:7-9

Orthodox Jewish Bible

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?