Isaiah the prophet presents King Hezekiah with a miraculous choice that alters the very laws of nature. This extraordinary event is meant to serve as absolute divine proof that God will heal the king from his illness, allowing him to go up to the House of God on the third day [מצודת דוד]. The miracle revolves entirely around the movement of the sun's shadow throughout the day. The primary approach among commentators is that the setting involves a terraced structure facing the sun, functioning as a sundial. On this structure, each step covered by the shadow marks a single hour of the day.
Isaiah offers Hezekiah a choice between two distinct supernatural occurrences regarding the future movement of this shadow. The first option is for the shadow to leap forward, unnaturally accelerating its regular course by ten steps in a single moment [מצודת דוד, רד״ק, חומת אנך, ביאור שטיינזלץ]. While this is the primary understanding, other perspectives offer different variations of this forward movement. One approach suggests that the shadow had already descended ten steps, and the prophet is asking if the king wishes for it to stop and remain exactly where it is for ten hours [רש״י]. Another view proposes that the shadow would continue to advance an additional ten steps along its regular path, completing a total movement of twenty steps [רלב״ג].
The second option presented to the king is for the shadow to travel backward, completely defying its natural course. This would effectively rewind the hours of the day, making it appear as though it were morning once again [רש״י, מצודת דוד]. The commentators explain a profound logic behind the choice between these two possibilities. Accelerating the sun's natural progression forward is viewed as a simpler miracle, as it still follows the normal direction of the celestial bodies. Conversely, halting the natural orbit and forcing the sun to retreat backward is considered a far more powerful, difficult, and wondrous sign. By presenting these alternatives, Isaiah gives Hezekiah the opportunity to select the greater and more undeniable miracle [רד״ק, חומת אנך].