Exodus 11:8-10

Young's Literal Translation

⁸ and all these thy servants have come down unto me, and bowed themselves to me, saying, Go out, thou and all the people who [are] at thy feet; and afterwards I do go out;' -- and he goeth out from Pharaoh in the heat of anger.

⁹ And Jehovah saith unto Moses, `Pharaoh doth not hearken unto you, so as to multiply My wonders in the land of Egypt;'

¹⁰ and Moses and Aaron have done all these wonders before Pharaoh, and Jehovah strengtheneth Pharaoh's heart, and he hath not sent the sons of Israel out of his land.