Exodus 8:3 - Matthew Poole's English Annotations on the Holy Bible

The river; under which are comprehended all other rivers, streams, and ponds, as appears from Exodus 8:5. But the river Nilus is mentioned, because God would make that an instrument of their misery in which they most gloried, Ezekiel 29:3, and to which they gave divine honours, and which was the instrument of their cruelty against the Israelites, Exodus 1:22. Into thy bed-chamber; either because God made the doors and windows to fly open, which it is easy to believe concerning God, seeing that this hath been many times done by evil angels; or because whensoever men entered into any house, or any room of their house, which their occasions would oft force them to do, the frogs, being always at their heels in great numbers, would go in with them. This plague was worse than the former, because it was more constant and more general; for the former was only in the waters, and did only molest them when they went to drink or use the water; but this infected all liquors, and all places, and at all times, and annoyed all their senses with their filthy substance, and shape, and noise, and stink, and mingled themselves with their meats, and sauces, and drinks, and crawling into their beds made them restless. And many of them probably were of a more ugly shape and infectious nature than ordinary.