Exodus 9:10-12

Young's Literal Translation

¹⁰ And they take the soot of the furnace, and stand before Pharaoh, and Moses sprinkleth it towards the heavens, and it is a boil [with] blains, breaking forth, on man and on beast;

¹¹ and the scribes have not been able to stand before Moses, because of the boil, for the boil hath been on the scribes, and on all the Egyptians.

¹² And Jehovah strengtheneth the heart of Pharaoh, and he hath not hearkened unto them, as Jehovah hath spoken unto Moses.