Exodus 16:23, 27-28

And he said unto them, This is that which Jehovah hath spoken, To-morrow is a solemn rest, a holy sabbath unto Jehovah: bake that which ye will bake, and boil that which ye will boil; and all that remaineth over lay up for you to be kept until the morning.

And it came to pass on the seventh day, that there went out some of the people to gather, and they found none. And Jehovah said unto Moses, How long refuse ye to keep my commandments and my laws?