In this thou shalt know, &c.— Words and signs had been hitherto unavailing with Pharaoh: Moses therefore is now commanded to stretch the awful rod of punishment over him; and to threaten him with such severe plagues, as should cause him to acknowledge that Jehovah, of whom he had said so tauntingly, who is Jehovah? I know him not, ch. Exodus 5:2.
The waters which are in the river—shall be turned to blood— The Author of the Book of Wisdom, ch. Exodus 2:6-7 observes, that this giving the Egyptians bloody water to drink, was for a manifest reproof of that commandment whereby the infants were slain in the water. It is not expressed how far this plague extended: the words of the text would lead one to believe, that all the water of the Nile was thus affected; from which three terrible evils ensued. All their fish, Exodus 7:18 which was their common food, died: the waters of the river corrupted and stunk; and thus were rendered unfit for drinking, as well as for all other ordinary uses. Ainsworth observes, that, in allusion to this plague, the contrary happiness of the Holy Land is described by the healing of the waters; so that all creatures shall live, and the fish be multiplied, Ezekiel 47:8-9. It is to be remembered, that none of these plagues affected the Israelites; and this tended still more to prove the power and providence of Jehovah.