Shemot 5:1-2

Orthodox Jewish Bible

5 And afterward Moshe and Aharon went in, and told Pharaoh, Thus saith Hashem Elohei Yisroel, Let My people go, that they may hold a chag (feast) unto Me in the midbar.

² And Pharaoh said, Who is Hashem, that I should obey His voice to let Yisroel go? I know not Hashem, neither will I let Yisroel go.