A boil - Means probably a burning tumor or carbuncle breaking out in pustulous ulcers. The miracle consisting in the severity of the plague and its direct connection with the act of Moses.

Shall be a boil - שחין shechin. This word is generally expounded, an inflammatory swelling, a burning boil; one of the most poignant afflictions, not immediately mortal, that can well affect the surface of the human body. If a single boil on any part of the body throws the whole system into a fever, what anguish must a multitude of them on the body at the same time occasion!

Breaking forth with blains - אבעבעת ababuoth, supposed to come from בעה baah, to swell, bulge out; any inflammatory swelling, node, or pustule, in any part of the body, but more especially in the more glandular parts, the neck, arm-pits, groin, etc. The Septuagint translate it thus: Και εσται ἑλκη φλυκτιδες αναζεουσαι· And it shalt be an ulcer with burning pustules. It seems to have been a disorder of an uncommon kind, and hence it is called by way of distinction, the botch of Egypt, Deuteronomy 28:27, perhaps never known before in that or any other country. Orosius says that in the sixth plague "all the people were blistered, that the blisters burst with tormenting pain, and that worms issued out of them." Alfred's Oros., lib. i., c. vii.

And it shall become small dust in all the land of Egypt,.... Which ashes, thrown up into the air, should be so multiplied and spread as to be over all the land of Egypt, and come down like showers of snow or sleet everywhere, only of a hot and scalding nature; or these handfuls of ashes were to be cast up into the air, and come down in the above manner, about Pharaoh's court, as a sign and token of what would be the case all over the kingdom:

and shall be a boil breaking forth with blains; that is, these ashes becoming a small dust, and falling down like the dew, snow, or sleet, yet hot and burning, should produce sore boils, burning ulcers, hot carbuncles, rising up in pustules, blisters, and buboes, which last word is pretty near in sound with the Hebrew word here used:

upon man, and upon beast, throughout all the land of Egypt; so that, as the last plague affected their property, substance, and riches, which in those times greatly lay in cattle, this, besides that, would affect their persons, and give them exceeding great pain, though it might not issue in death.

And it shall become small dust in all the land of Egypt, and shall be a boil breaking forth with blains upon man, and upon beast, throughout all the land of Egypt.

9:9 A boil breaking forth with blains - A burning scab, which quickly raised blisters and blains.

9:8-12 When the Egyptians were not wrought upon by the death of their cattle, God sent a plague that seized their own bodies. If lesser judgments do not work, God will send greater. 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 a terror to them. The plague itself was very grievous. The magicians themselves were struck with these boils. Their power was restrained before; but they continued to withstand Moses, and to confirm Pharaoh in his unbelief, till they were forced to give way. Pharaoh continued obstinate. He had hardened his own heart, and now God justly gave him up to his own heart's lusts, permitting Satan to blind and harden him. If men shut their eyes against the light, it is just with God to close their eyes. This is the sorest judgment a man can be under out of hell.