Exodus 9:8-12

Then the LORD said to Moses and Aaron, “Take for yourselves handfuls of soot from a kiln, and let Moses throw it toward the sky in the sight of Pharaoh. It will become fine dust over all the land of Egypt, and will become boils breaking out with sores on man and beast through all the land of Egypt.” So they took soot from a kiln, and stood before Pharaoh; and Moses threw it toward the sky, and it became boils breaking out with sores on man and beast. The magicians could not stand before Moses because of the boils, for the boils were on the magicians as well as on all the Egyptians. And the LORD hardened Pharaoh’s heart, and he did not listen to them, just as the LORD had spoken to Moses.