Charles Ellicott Commentary 2 Kings 20:9

"And Isaiah said, This shall be the sign unto thee from Jehovah, that Jehovah will do the thing that he hath spoken: shall the shadow go forward ten steps, or go back ten steps?" — 2 Kings 20:9 (ASV)

Shall the shadow go forward ten degrees, or go back ten degrees? —Rather, the shadow has marched (or travelled) ten steps; shall it return ten steps? This is what the Hebrew text seems to say at first glance. But Hezekiah’s answer apparently implies an alternative; and we might render: “the shadow shall have travelled ten steps; or shall it return ten steps?” (Compare the Septuagint πορεύσεται.) The Targum has: “shall the shadow march ten hours or return ten hours?” The Vulgate also makes it a double question. The Syriac is: “the shadow shall march ten steps, or return ten steps.”

It is very probable that the Hebrew text is corrupt. We might read the first word as an infinitive instead of a perfect, after the analogy of 2 Kings 19:29 (ye shall eat). Or we might read “shall it march?” as a question (hă-yēləḵ); or better still, “shall it go up” (hă-ya‘ăleh), after the hint afforded by the Vulgate: “Vis ut ascendat umbra ... Et ait Ezechias, Facile est umbram crescere,” etc. It is obvious that a kind of sun-dial is meant, though what kind is not so clear. The word “degrees” (ma‘ălôth) means “steps” or “stairs” wherever it occurs. (Ezekiel 40:6; Ezekiel 40:22; Ezekiel 40:26; Ezekiel 40:31, etc.; 1 Kings 10:20; Nehemiah 3:15.)

There is probability, therefore, in Knobel’s conjecture that “the dial of Ahaz” consisted of a column rising from a circular flight of steps, so as to throw the shadow of its top on the top step at noon, and morning and evening on the bottom step. This, or some similar device, was set up in the palace court, and was probably visible to Hezekiah lying on his sick bed and facing the window.

Herodotus (ii. 9) ascribes the invention of the gnomon to the Babylonians. From the inscriptions we know that they divided time into periods of two hours, each called in Sumerian kasbumi, and in Assyrian aslu. Each kasbu or aslu was subdivided into sixty equal parts.