Exodus 16:21

To wit, as much of it as was left upon the ground. This was not from its own nature, which was so solid that it could endure the fire, and was bruised by a pestle; but from God's wise providence, partly, that it might not be corrupted or trodden under foot, or otherwise abused, and so despised; partly, that it might not remain there to tempt any of them to gather more of it than they should; and partly, that all their stock of provision being wasted, they might be obliged to the more entire dependence upon God. And this is here mentioned as a reason why they gathered it in the morning.