Exodus 9:6-9

6And the Lord did just as he had said. The next morning all the livestock of the Egyptians died, but the Israelites didn’t lose a single animal.

7Pharaoh sent his officials to investigate, and they discovered that the Israelites had not lost a single animal! But even so, Pharaoh’s heart remained stubborn, and he still refused to let the people go.

8Then the Lord said to Moses and Aaron, “Take handfuls of soot from a brick kiln, and have Moses toss it into the air while Pharaoh watches.

9The ashes will spread like fine dust over the whole land of Egypt, causing festering boils to break out on people and animals throughout the land.”