מלכים ב, פרק כ׳, פסוק י׳

King Hezekiah seeks absolute certainty regarding his promised recovery. Offered a choice of how a shadow might move as a divine sign, he carefully weighs which option would provide the most undeniable proof of heavenly intervention. He demands a miracle that completely shatters the known laws of nature, dismissing the idea of the shadow advancing forward as too simple or unconvincing.

The primary approach among commentators is that a shadow moving forward, even at an unusually rapid pace, still follows the natural, expected trajectory of the sun. Because this acceleration might not be clearly noticeable to the naked eye, it lacks the absolute certainty the king desires. Instead, he insists that the shadow reverse its course. A shadow moving backward serves as a far more powerful and wondrous sign, creating a startling reality where the afternoon suddenly reverts to morning [רש״י, מצודת דוד, ביאור שטיינזלץ].

However, this request raises a significant question. How could the king refer to any alteration in the movement of celestial bodies as a simple or easy feat? Altering the sun's actual path is a colossal miracle, arguably greater than those performed by Moses. Dismissing such an event as easy seems to severely underestimate the magnitude of the wonder.

To resolve this difficulty, a different perspective suggests that the miracle did not alter the sun itself, but only affected the shadow on the earth. According to this explanation, the movement of clouds and vapors beneath the sun can refract light and shift a shadow from its normal position. Hezekiah observed that the wind direction at that moment could naturally push the clouds and accelerate the shadow forward. Because this could be mistaken for a normal weather phenomenon, he considered it a weak proof. To establish beyond any doubt that this was a genuine sign from God, he asked for the shadow to move backward, directly against the prevailing wind. In response, God miraculously generated vapors that swept rapidly in the opposite direction, catching the sunlight and instantly forcing the shadow backward [רלב״ג].