Exodus 9:8-10

Take you handfuls of the ashes of the furnace Sometimes God shows men their sin in their punishment. They had oppressed Israel in the furnaces, and now the ashes of the furnace are made as much a terror to them as ever their task masters had been to the Israelites. “The matter of this plague,” says Ainsworth, “is from the fire, which also being one of the elements they deified, is here made the instrument of evil to them, and reclaimed by Jehovah to his service, in punishment of its deluded votaries, who worshipped the creature more than the Creator.” A former miracle was from water, and the next from air, to show that God rules in all. It became a bile A sore, angry swelling, or inflammation; breaking forth with blains Or blisters, quickly raised; upon man and upon beast

Thus we see that the men themselves were smitten after the cattle, which is agreeable to the method of Providence in punishing, first sending previous afflictions to warn mankind, that they may shun greater evils by timely repentance. This bile is afterward called the botch of Egypt, (Deuteronomy 28:27,) as if it were some new disease, never heard of before, and known ever after by that name.