Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Exo 7:1-7) Moses and Aaron encouraged.
(Exo 7:8-13) The rods turned into serpents, Pharaoh's heart is hardened.
(Exo 7:14-25) The river is turned into blood, The distress of the Egyptians.
God glorifies himself. He makes people know that he is Jehovah. Israel is made to know it by the performance of his promises to them, and the Egyptians by the pouring out of his wrath upon them. Moses, as the ambassador of Jehovah, speaking in his name, laid commands upon Pharaoh, denounced threatenings against him, and called for judgments upon him. Pharaoh, proud and great as he was, could not resist. Moses stood not in awe of Pharaoh, but made him tremble. This seems to be meant in the words, Thou shalt be a god unto Pharaoh. At length Moses is delivered from his fears. He makes no more objections, but, being strengthened in faith, goes about his work with courage, and proceeds in it with perseverance.
What men dislike, because it opposes their pride and lusts, they will not be convinced of; but it is easy to cause them to believe things they wish to be true. God always sends with his word full proofs of its Divine authority; but when men are bent to disobey, and willing to object, he often permits a snare to be laid wherein they are entangled. The magicians were cheats, trying to copy the real miracles of Moses by secret sleights or jugglings, which to a small extent they succeeded in doing, so as to deceive the bystanders, but they were at length obliged to confess they could not any longer imitate the effects of Divine power. None assist more in the destruction of sinners, than such as resist the truth by amusing men with a counterfeit resemblance of it. Satan is most to be dreaded when transformed into an angel of light.
Here is the first of the ten plagues, the turning of the water into blood. It was a dreadful plague. The sight of such vast rolling streams of blood could not but strike horror. Nothing is more common than water: so wisely has Providence ordered it, and so kindly, that what is so needful and serviceable to the comfort of human life, should be cheap and almost every where to be had; but now the Egyptians must either drink blood, or die for thirst. Egypt was a pleasant land, but the dead fish and blood now rendered it very unpleasant. It was a righteous plague, and justly sent upon the Egyptians; for Nile, the river of Egypt, was their idol. That creature which we idolize, God justly takes from us, or makes bitter to us. They had stained the river with the blood of the Hebrews' children, and now God made that river all blood. Never any thirsted after blood, but sooner or later they had enough of it. It was a significant plague; Egypt had great dependence upon their river, Zac 14:18; so that in smiting the river, they were warned of the destruction of all the produce of their country. The love of Christ to his disciples changes all their common mercies into spiritual blessings; the anger of God towards his enemies, renders their most valued advantages a curse and a misery to them. Aaron is to summon the plague by smiting the river with his rod. It was done in the sight of Pharaoh and his attendants, for God's true miracles were not performed as Satan's lying wonders; truth seeks no corners. See the almighty power of God. Every creature is that to us which he makes it to be water or blood. See what changes we may meet with in the things of this world; what is always vain, may soon become vexatious. See what mischievous work sin makes. If the things that have been our comforts prove our crosses, we must thank ourselves. It is sin that turns our waters into blood. The plague continued seven days; and in all that time Pharaoh's proud heart would not let him desire Moses to pray for the removal of it. Thus the hypocrites in heart heap up wrath. No wonder that God's anger is not turned away, but that his hand is stretched out still.