And Pharaoh said, Who is the LORD, that I should obey his voice to let Israel go? I know not the LORD, neither will I let Israel go.
Pharaoh said, Who is the Lord? - rather, "Yahweh." Lord was a common name applied to objects of worship; but Yahweh was a name the king of Egypt had never heard of. He estimated the character and power of this God by the abject and miserable condition of the worshippers, and concluded that He held as low a rank among the gods as His people did in the nation. To demonstrate the supremacy of the true God over all the gods of Egypt was the design of the plagues that were inflicted on the land.
Neither will I let Israel go. Since Pharaoh's honour and interest were both involved, he determined to crush this attempt, and, in a tone of insolence, or perhaps profanity, rejected the request for the release of the Hebrew slaves.