Exodus 9:8-12

And the LORD said to Moses and Aaron, “Take handfuls of soot from the kiln, and let Moses throw them in the air in the sight of Pharaoh. It shall become fine dust over all the land of Egypt, and become boils breaking out in sores on man and beast throughout all the land of Egypt.” So they took soot from the kiln and stood before Pharaoh. And Moses threw it in the air, and it became boils breaking out in sores on man and beast. And the magicians could not stand before Moses because of the boils, for the boils came upon the magicians and upon all the Egyptians. But the LORD hardened the heart of Pharaoh, and he did not listen to them, as the LORD had spoken to Moses.