(17) In this thou shalt know that I am the Lord.--See the comment on Exodus 7:5.

The rod that is in my hand, i.e., "in the hand of my servant." God is here represented as about to do that which was actually done by Aaron (Exodus 7:20). "Qui facit per alium, facit per se."

Verse 17. - In this thou shalt know that I am the Lord. Pharaoh had declared on the occasion specially referred to, "I know not Jehovah, neither will I let Israel go" (Exodus 5:2). He is now told that he shall "know Jehovah" in the coming visitation; he shall know, i.e., that there is a great and truly existent God who controls nature, does as he will even with the Nile, which the Egyptians regarded as a great deity; and can turn, if he see fit, the greatest blessings into curses. Behold, I will smite. God here speaks of the acts of Moses and Aaron as his own acts, and of their hands as his hand, because they were mere instruments through which he worked. The Roman law said: "Qui facit per alium, tacit per se." The waters... shall be turned to blood. Not simply, "shall be of the colour of blood," as Rosenmuller paraphrases, but shall become and be, to all intents and purposes, blood. It is idle to ask whether the water would have answered to all the modern tests, microscopic and other, by which blood is known. The question cannot be answered. An that we are entitled to conclude from the words of the text is, that the water had all the physical appearance the look, taste, smell, texture of blood: and hence, that it was certainly not merely discoloured by the red soil of Abyssinia, nor by cryptegamic plants and infusoria. Water thus changed would neither kill fish, nor "stink," nor be utterly undrinkable.

7:14-25 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, Zec 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.Thus saith the Lord, in this thou shalt know that I am the Lord,.... By the following instance of his power and vengeance:

behold, I will smite with the rod that is in my hand; which though in the hand of Moses, Exodus 7:18 yet he being his ambassador, and representing him, is said to be in the hand of the Lord; and with this he threatens to smite

upon the waters which are in the river; the river Nile, and the canals thereof:

and they shall be turned to blood; and if this river was their god, it would abundantly appear that the God of the Hebrews was Jehovah, and above all gods, and particularly above theirs.