Notes on the Bible, by Albert Barnes, [1834], at sacred-texts.com
With this chapter begins the series of miracles performed in Egypt. They are progressive. The first miracle is performed to accredit the mission of the brothers; it is simply credential, and unaccompanied by any infliction. Then come signs which show that the powers of nature are subject to the will of Yahweh, each plague being attended with grave consequences to the Egyptians, yet not inflicting severe loss or suffering; then in rapid succession come ruinous and devastating plagues, murrain, boils, hail and lightning, locusts, darkness, and lastly, the death of the firstborn. Each of the inflictions has a demonstrable connection with Egyptian customs and phenomena; each is directly aimed at some Egyptian superstition; all are marvelous, not, for the most part, as reversing, but as developing forces inherent in nature, and directing them to a special end. The effects correspond with these characteristics; the first miracles are neglected; the following plagues first alarm, and then for a season, subdue, the king, who does not give way until his firstborn is struck. Even that blow leaves him capable of a last effort, which completes his ruin, and the deliverance of the Israelites.
I have made thee a god - Or "appointed thee." See the margin reference. Moses will stand in this special relation to Pharaoh, that God will address him by a prophet, i. e. by one appointed to speak in His name. The passage is an important one as illustrating the primary and essential characteristic of a prophet, he is the declarer of God's will and purpose.
Wonders - A word used only of portents performed to prove a divine interposition; they were the credentials of God's messengers.
Thy rod - Apparently the rod before described Exo 4:2, which Moses on this occasion gives to Aaron as his representative.
A serpent - A word different from that in Exo 4:3. Here a more general term, תנין tannı̂yn, is employed, which in other passages includes all sea or river monsters, and is more specially applied to the crocodile as a symbol of Egypt. It occurs in the Egyptian ritual, nearly in the same form, "Tanem," as a synonym of the monster serpent which represents the principle of antagonism to light and life.
Three names for the magicians of Egypt are given in this verse. The "wise men" are men who know occult arts. The "sorcerers" are they who "mutter magic formulae," especially when driving away crocodiles, snakes, asps, etc. It was natural that Pharaoh should have sent for such persons. The "magicians" are the "bearers of sacred words," scribes and interpreters of hieroglyphic writings. Books containing magic formulae belonged exclusively to the king; no one was permitted to consult them but the priests and wise men, who formed a council or college, and were called in by the Pharaoh on all occasions of difficulty.
The names of the two principal magicians, Jannes and Jambres, who "withstood Moses," are preserved by Paul, Ti2 3:8. Both names are Egyptian.
Enchantments - The original expression implies a deceptive appearance, an illusion, a juggler's trick, not an actual putting forth of magic power. Pharaoh may or may not have believed in a real transformation; but in either case he would naturally consider that if the portent performed by Aaron differed from that of the magicians, it was a difference of degree only, implying merely superiority in a common art. The miracle which followed Exo 7:12 was sufficient to convince him had he been open to conviction. It was a miracle which showed the truth and power of Yahweh in contrast with that of others.
And he hardened - Or Pharaoh's heart was hardened. See Exo 4:21.
He goeth out unto the water - The Nile was worshipped under various names and symbols; at Memphis especially, as Hapi, i. e. Apis, the sacred bull, or living representation of Osiris, of whom the river was regarded as the embodiment or manifestation. If, as is probable, the king went to offer his devotions, the miracle would have special force and suitableness. It was also the season of the yearly overflowing, about the middle of June; and the daily rise of the water was accurately recorded, under the personal superintendence of the king. In early inscriptions the Nilometer is the symbol of stability and providential care.
Turned to blood - This miracle would bear a certain resemblance to natural phenomena, and therefore be one which Pharaoh might see with amazement and dismay, yet without complete conviction. It is well known that before the rise the water of the Nile is green and unfit to drink. About the 25th of June it becomes clear, and then yellow, and gradually reddish like ochre; an effect due to the presence of microscopic cryptogams and infusoria. The supernatural character of the visitation was tested by the suddenness of the change, by its immediate connection with the words and act of Moses, and by its effects. It killed the fish, and made the water unfit for use, neither of which results follows the annual discoloration.
Shall lothe - The water of the Nile has always been regarded by the Egyptians as a blessing unique to their land. It is the only pure and wholesome water in their country, since the water in wells and cisterns is unwholesome, while rain water seldom falls, and fountains are extremely rare.
The "streams" mean the natural branches of the Nile in Lower Egypt. The word "rivers" should rather be "canals"; they were of great extent, running parallel to the Nile, and communicating with it by sluices, which were opened at the rise, and closed at the subsidence of the inundation. The word rendered "ponds" refers either to natural fountains, or more probably to cisterns or tanks found in every town and village. The "pools", literally "gathering of waters," were the reservoirs, always large and some of enormous extent, containing sufficient water to irrigate the country in the dry season.
In vessels of wood - The Nile water is kept in vessels and is purified for use by filtering, and by certain ingredients such as the paste of almonds.
The fish ... - The Egyptians subsisted to a great extent on the fish of the Nile, though salt-water fish were regarded as impure. A mortality among the fish was a plague that was much dreaded.
Seven days - This marks the duration of the plague. The natural discoloration of the Nile water lasts generally much longer, about 20 days.