Exodus 9:6-9

6So the Lord did this thing on the next day, and all the livestock of Egypt died; but of the livestock of the children of Israel, not one died.

7Then Pharaoh sent, and indeed, not even one of the livestock of the Israelites was dead. But the heart of Pharaoh became hard, and he did not let the people go.

8So the Lord said to Moses and Aaron, “Take for yourselves handfuls of ashes from a furnace, and let Moses scatter it toward the heavens in the sight of Pharaoh.

9And it will become fine dust in all the land of Egypt, and it will cause boils that break out in sores on man and beast throughout all the land of Egypt.”