Shemot 10:1-2

And Hashem said unto Moshe, Go in unto Pharaoh; for I have hardened his lev, and the lev of his avadim, that I might show these My otot before him; And that thou mayest tell in the ears of thy ben, and of thy benʼs ben, what things I have wrought in Mitzrayim, and My otot which I have done among them; that ye may have da'as that I am Hashem.