The Mekhilta DeRabbi Yishmael tackled a precise question about the manna's daily lifecycle. (Exodus 16:21) states that "when the sun was hot, it melted." But what time of day does "when the sun was hot" actually mean?
The rabbis proposed the fourth hour of the day, roughly ten o'clock in the morning by modern reckoning. The Jewish day was divided into twelve hours from sunrise to sunset, making the fourth hour the point when the morning sun had been climbing for several hours but had not yet reached its peak.
But why the fourth hour and not the sixth, which is noon and the hottest part of the day? The Mekhilta's answer is elegant. The phrase "when the sun was hot" implies a specific condition: the sun-exposed ground was hot, but shaded areas were still cool. At noon, everything is hot. Both sun and shade become oppressive in the desert heat. Only in the fourth hour does a clear temperature difference exist between sunny and shaded spots.
This distinction matters because it reveals God's precise engineering of the manna miracle. The Israelites had from dawn until roughly ten in the morning to gather their daily portion. After that, the uncollected manna melted away. God did not leave the manna sitting on the ground all day where it might be hoarded, fought over, or trampled. He gave Israel a defined window of opportunity, generous enough for the diligent but firm enough to enforce trust. Those who gathered early had plenty. Those who waited too long found nothing but streams of melted manna running across the desert floor.