Exodus 8:7 - Clarke's commentary and critical notes on the Bible

And the magicians did so with their enchantments, and brought up frogs upon the land of Egypt. The magicians did so - A little juggling or dexterity of hand might have been quite sufficient for the imitation of this miracle, because frogs in abundance had already been produced; and some of these kept in readiness might have been brought forward by the magicians, as proofs of their pretended power and equality in influence to Moses and Aaron.