Deuteronomy 28:27

27.The Lord will smite thee with the botch of Egypt. Whether you understand this passage of the extraordinary plagues which God inflicted on the Egyptians at the time of His people’s deliverance, or of the ordinary diseases which had before prevailed among them, though the latter is more probable, still Moses signifies, that whilst the Egyptians were smitten with these plagues, God’s people escaped them, in order that this distinction might more clearly represent His favor. For it could not happen naturally that in the same place the diseases, from which the Israelites were free, should afflict the Egyptians alone. God therefore threatens, that if they should despise His Law, He would deal with them as they had seen Him deal with heathen nations. And assuredly, since God then chose to multiply His people miraculously, it can be by no means doubted but that He wonderfully privileged them by the bestowment of health and rigor. It is doubtful whether by diseases of the fundament He signifies hemorrhoids or prolapsus, or some other secret disease, such as that which attacked the Philistines when they captured the ark of the covenant. (1 Samuel 5:6.) He subjoins other diseases, in which there appear special marks of God’s wrath; for although they sometimes affect the children of God also, still I have shewn elsewhere that the same punishments are so dealt out to them respectively, that they widely differ from each other. When Job was smitten with terrible ulcers, so as to become corrupt, he seemed for a time to present the marks of a reprobate person; but what in that holy man was an exercise of patience, is in the transgressors of the Law the just reward of their crimes by the curse of God.