ישעיהו, פרק ל״ח, פסוק ז׳

A sudden promise of recovery can be difficult to accept when standing at the edge of death. King Hezekiah is trapped in a state of extreme physical weakness, certain that his end is near. When the prophet Isaiah brings the news that the king will heal and receive additional years of life, the contrast between his grim reality and this hopeful promise is overwhelming. Such a dramatic and unexpected reversal requires immediate, tangible proof that the healing will actually take place [ביאור שטיינזלץ]. A practical miracle is therefore provided as a direct response to the king's own request for evidence that he will fully recover [רש״י].

The full scope of this miracle is clarified through a related dialogue, where Isaiah offers the king a choice: the daytime shadow can move ten degrees forward or ten degrees backward. The king rejects the forward movement as too simple and specifically asks for the shadow to retreat. The timing of this event is crucial to understanding his choice, as the conversation takes place merely two hours before sunset.

If the shadow were to advance ten degrees forward, the sun itself could not participate in the event. Moving forward by that amount would push the time into the night, a period when shadows do not naturally exist. Therefore, advancing the shadow would only be a local occurrence, resulting in a mere manipulation of the shade without any actual shift in the sun's position. By demanding that the shadow move backward, the king ensures that the sun must travel eastward along with it. This choice guarantees that the event is not just a minor visual effect, but an absolute intervention by God in the natural world, forcing the sun itself to change its course and reverse its path [מלבי״ם].