Exodus 16:4-6

Then said Jehovah unto Moses, Behold, I will rain bread from heaven for you; and the people shall go out and gather a day’s portion every day, that I may prove them, whether they will walk in my law, or not. And it shall come to pass on the sixth day, that they shall prepare that which they bring in, and it shall be twice as much as they gather daily. And Moses and Aaron said unto all the children of Israel, At even, then ye shall know that Jehovah hath brought you out from the land of Egypt