Exodus 9:8-10

8Then the Lord said to Moses and Aaron, ‘Take in your hands some ashes from an oven. Throw them up in the air as Pharaoh watches.

9They will become very small dust over the whole country of Egypt. The dust will cause boils to appear on the skin of people and animals. It will happen all over Egypt.’

10So they took ashes from an oven and they stood in front of Pharaoh. Moses threw the ashes up in the air. Then bad boils appeared on both people and animals.