Exodus 16:31

The LORD said to Moses, “How long do you refuse to keep my commandments and my laws?

Behold, because the LORD has given you the Sabbath, therefore he gives you on the sixth day the bread of two days. Everyone stay in his place. Let no one go out of his place on the seventh day.”

So the people rested on the seventh day.

Moses said, “This is the thing which the LORD has commanded, ‘Let an omer-full of it be kept throughout your generations, that they may see the bread with which I fed you in the wilderness, when I brought you out of the land of Egypt.’”

Moses said to Aaron, “Take a pot, and put an omer-full of manna in it, and lay it up before the LORD, to be kept throughout your generations.”

As the LORD commanded Moses, so Aaron laid it up before the Testimony, to be kept.