Charles Ellicott Commentary Exodus 9:10

"And they took ashes of the furnace, and stood before Pharaoh; and Moses sprinkled it up toward heaven; and it became a boil breaking forth with blains upon man and upon beast." — Exodus 9:10 (ASV)

Moses sprinkled it up toward heaven. —Presenting it, as it were, to God, in evidence of His people’s wrongs.

A boil breaking forth with sores. —Hebrew: an inflammation, producing pustules. Diseases of this character are not uncommon in Egypt , but they are not often very severe, nor do they attack man and beast indiscriminately. The miraculous character of the plague was shown:

1. by its being announced beforehand;
2. by its severity (Exodus 9:11);
3. by its universality (Exodus 9:11); and
4. by its extension to animals.