Exodus 15:12

Thou stretchedst out Thy right hand, the earth swallowed them. The miracles which the Lord had performed in Egypt and upon the host of the Egyptians showed that a similar fate awaits all the enemies of the Lord, that no man can stand before Him as His opponent.

I have heard the murmurings of the children of Israel. Speak unto them, saying, At even ye shall eat flesh, between the evenings, at twilight, before nightfall, and in the morning ye shall be filled with bread; and ye shall know that I am the Lord, your God. It would be another unmistakable proof of His almighty power.