And Pharaoh turned. In this word Moses teaches us that the hardness of heart, to which God had devoted Pharaoh, was voluntary; so that the sin rested in himself, nor did the secret appointment of God avail anything to lessen his culpability, for his folly is condemned, because he did not "set his heart to this also." Whence it follows that he was the author of his own obstinacy, because, being blinded by pride and contempt, he took no account of the glory of God. Thus the wicked, although as being vessels of wrath, they are cast of God into a reprobate mind, still harden themselves, because wittingly and willfully they run against God, and thus their security, audacity, and perverseness take away from them the excuse of ignorance or error. Wherefore this example warns us not to slumber when God arouses us, but attentively to consider His works, which may instruct us to reverence and fear Him. The statement that the Egyptians dug wells for themselves increases the certainty of the miracle, as does also what is added as to the seven days; for if the corruption of the water had only been momentary, some suspicion of delusion might have crept in, which was removed both by the continued taste and appearance. Therefore it was said before, that the Egyptians would suffer inconvenience and pain [1] from the want of water; for thus I explain it, that they should be sorrowful and afflicted, viz., because they had nothing to drink.

Footnotes

1 - He seems to allude to verse 18, which he translates "et molestia afficientur Aegyptii, bibendo aquas ex flumine."

And Pharaoh turned, and went into his house,.... Turned away from Moses and Aaron, and turned back from the river to which he came, and went to his palace in the city; it being perhaps now about dinner time, when all before related had passed:
neither did he set his heart to this also: had no regard to this miracle of turning the waters into blood, as well as he had none to the rod being turned into a serpent, and devouring the rods of the magicians; he neither considered the one nor the other, or seriously and closely thought of this, any more than of the other.