Exodus 10:3 (KJV)

And the LORD said unto Moses, Go in unto Pharaoh: for I have hardened his heart, and the heart of his servants, that I might shew these my signs before him:

And that thou mayest tell in the ears of thy son, and of thy son's son, what things I have wrought in Egypt, and my signs which I have done among them; that ye may know how that I am the LORD.

Else, if thou refuse to let my people go, behold, to morrow will I bring the locusts into thy coast:

And they shall cover the face of the earth, that one cannot be able to see the earth: and they shall eat the residue of that which is escaped, which remaineth unto you from the hail, and shall eat every tree which groweth for you out of the field:

And they shall fill thy houses, and the houses of all thy servants, and the houses of all the Egyptians; which neither thy fathers, nor thy fathers' fathers have seen, since the day that they were upon the earth unto this day. And he turned himself, and went out from Pharaoh.

And Pharaoh's servants said unto him, How long shall this man be a snare unto us? let the men go, that they may serve the LORD their God: knowest thou not yet that Egypt is destroyed?

And Moses and Aaron were brought again unto Pharaoh: and he said unto them, Go, serve the LORD your God: but who are they that shall go?