Shemot 7:3-4

And I will harden the lev Pharaoh, and multiply My Otot and My Mofetim in Eretz Mitzrayim. But Pharaoh shall not pay heed unto you, that I may lay My yad upon Mitzrayim, and bring forth Mine tzve'os, and My people the Bnei Yisroel, out of Eretz Mitzrayim by shefatim gedolim (great judgments).