Exodus 16:4-6

4Then said Jehovah to Moses, Behold, I will rain bread from heaven for you; and the people shall go out and gather the daily need on its day, that I may prove them, whether they will walk in my law, or not.

5And it shall come to pass on the sixth day, that they shall prepare what they have brought in; and it shall be twice as much as they shall gather daily.

6And Moses and Aaron said to all the children of Israel, In the evening, then shall ye know that Jehovah has brought you out from the land of Egypt;