Exodus 10:1-2

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