Exodus 9:10-12

Amplified Bible

¹⁰ So they took soot from the kiln, and stood before Pharaoh; and Moses threw it toward the sky, and it became boils erupting in sores on man and animal. ¹¹ The magicians (soothsayer-priests) could not stand before Moses because of the boils, for the boils were on the magicians as well as on all the Egyptians. ¹² But the Lord hardened the heart of Pharaoh, and he did not listen or pay attention to them, just as the Lord had told Moses.