New Defender's Study Bible Notes
8:3 bring forth frogs. It is possible that the poisoned waters somehow caused a multiplication of frogs in the river’s marshes and pools, which then emerged to infest the land. The frog also was worshipped by the Egyptians, in the form of the frog goddess Hekt.
8:7 the magicians did so. Pharaoh’s magicians were somehow able to duplicate the first two plagues. Whether this was by means of demonic power or by deception is not stated. More likely it was the latter, just as with the serpents, since neither Satan nor his fallen angels are able to create (only God is the Creator), but they are deceivers, and able to generate deceptive hallucinations in the minds of those who desire to reject God and His will. Furthermore, it is noteworthy that the magicians were unable either to cure the waters or disperse the frogs, which Pharaoh would certainly have preferred to their merely mimicking Moses.
8:16 become lice. The third plague followed when Aaron’s rod of judgment smote the dust, and small insects (lice, or possibly gnats) swarmed forth from the dust throughout the land. This was a miracle the magicians could not imitate, and even they had to acknowledge that it was from God (Exodus 8:19).
8:19 the finger of God. Egyptian magical texts occasionally refer to “the finger of” one of their gods or goddesses. Here they recognize the miracle as emanating from the finger of the true God of creation.
8:21 swarms of flies. This fourth plague, like some of the others, was a fairly common experience in Egypt, though never before of this magnitude.
8:23 a division. The remaining miracles not only were utterly beyond the abilities of either men or demons to perform or imitate, but also further demonstrated by this divinely ordained selectivity by the true God behind the miracles. Each judgment, in fact, in some way directly “mocked” the impotent gods of Egypt.