Here is a plain allusion to the plagues which God brought upon Pharaoh king of Egypt for his oppression of his ancient Israel; God hereby showing us, that he would deal by this Romish beast for his persecutions of his gospel churches, as he dealt by Pharaoh: as he turned the Egyptian rivers into blood, so as the fish died, and the waters stunk, Exodus 7:20,21, and as he plagued the Egyptians with boils and blains, Exodus 9:9; so he would plague the papacy by proportionable judgments, until, as Pharaoh with his whole party was at last drowned in the Red Sea, so all the antichristian party shall be rooted out. Here are two of the Egyptian plagues mentioned, but this vision begins with the sixth of the Egyptian plagues, viz. that of boils breaking out in blains. What is meant by this grievous sore I must profess myself not to understand, but think Dr. More speaks very probably, interpreting it of trouble and vexation, which the popish party should have upon the first prospect of their kingdom's going down; it being of the nature of sores to vex and disturb those that are affected with them, so as they are very uneasy so long as they are affected with them. And, indeed, I find many interpreters agree in this notion.
Related Commentaries of Revelation 16:2
Revelation 16:2
2 And the first went, and poured out his vial upon the earth; and there fell a noisome and grievous sore upon the men which had the mark of the beast, and upon them which worshipped his image.