Exodus 9:8, 10-11

So 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.

Then they took ashes from the furnace and stood before Pharaoh, and Moses scattered them toward heaven. And they caused boils that break out in sores on man and beast. And the magicians could not stand before Moses because of the boils, for the boils were on the magicians and on all the Egyptians.