Exodus 16:1-5

They set out from Elim, and all the congregation of Israel came to the Wilderness of Sin, which is between Elim and Sinai, on the fifteenth day of the second month after they left the land of Egypt. The whole congregation of the Israelites [grew discontented and] murmured and rebelled against Moses and Aaron in the wilderness, and the Israelites said to them, “Would that we had died by the hand of the LORD in the land of Egypt, when we sat by the pots of meat and ate bread until we were full; for you have brought us out into this wilderness to kill this entire assembly with hunger.” Then the LORD said to Moses, “Behold, I will cause bread to rain from heaven for you; the people shall go out and gather a day’s portion every day, so that I may test them [to determine] whether or not they will walk [obediently] in My instruction (law). And it shall be that on the sixth day, they shall prepare to bring in twice as much as they gather daily [so that they will not need to gather on the seventh day].”