יונה, פרק ד׳, פסוק ז׳

The comforts and pleasures of this world are fleeting. Just as they can appear suddenly, they are liable to vanish quickly [אברבנאל]. Jonah experienced only a single day of joy and relief in the shade of his plant. The very next day, immediately following his brief happiness [אבן עזרא, מצודת דוד], God specially arranged for a worm to appear at that exact location [רד״ק]. This occurred at the break of dawn, with the very first sparkling light in the eastern sky before the sun actually rose [מצודת ציון].

The newly appointed creature then attacked the plant. The primary approach among commentators is that the worm severed the plant from below at its root, cutting off its ability to draw moisture from the earth. Alternatively, some explain that the worm simply ate the plant [ביאור שטיינזלץ]. Regardless of the exact method, the result was immediate. Severed from its life source, the plant ceased to grow. The leaves that had provided Jonah with such welcome shade quickly dried up and fell away under the heat of the sun [מצודת דוד, רד״ק, ביאור שטיינזלץ].