Shemoth (Exodus) 10:1-2

And יהוה said to Mosheh, “Go in to Pharaoh, for I have hardened his heart and the hearts of his servants, so that I show these signs of Mine before him, and that you relate in the hearing of your son and your son’s son what I have done in Mitsrayim, and My signs which I have done among them. And you shall know that I am יהוה.”