They were piled into countless heaps, and there was a terrible stench in the land.
Pharaoh is here first threatened and then plagued with frogs, as afterwards, in this chapter, with lice and flies, little despicable inconsiderable animals, and yet by their vast numbers rendered sore plagues to the Egyptians. God could have plagued them with lions, or bears, or wolves, or with vultures or other birds of prey; but he chose to do it by these contemptible instruments. 1.
Commenting on Exodus 8:1-15
But when Pharaoh saw that there was respite,.... From his affliction, as the Targum of Jonathan adds; the plague was removed, and he found himself and his people at ease: or there was a "breathing" (c); before he and his people were so oppressed, that they could scarce breathe, but now being delivered from the judgment on them with which they were straitened, were enlarged...
They gathered them together upon heaps - The killing of the frogs was a mitigation of the punishment; but the leaving them to rot in the land was a continual proof that such a plague had taken place, and that the displeasure of the Lord still continued.