Adam Clarke's Commentary on the Bible - Exodus 7:15
Lo, he goeth out unto the water - Probably for the purpose of bathing, or of performing some religious ablution. Some suppose he went out to pay adoration to the river Nile, which was an object of religious worship among the ancient Egyptians. "For," says Plutarch, De Iside., ουδεν οὑτω τιμη Αιγυπτιοις ὡς ὁ Νειλος "nothing is in greater honor among the Egyptians than the river Nile." Some of the ancient Jews supposed that Pharaoh himself was a magician, and that he walked by the river... read more
Adam Clarke's Commentary on the Bible - Exodus 7:14
Pharaoh's heart is hardened - כבד cabed , is become heavy or stupid; he receives no conviction, notwithstanding the clearness of the light which shines upon him. We well know the power of prejudice: where persons are determined to think and act after a predetermined plan, arguments, demonstrations, and even miracles themselves, are lost on them, as in the case of Pharaoh here, and that of the obstinate Jews in the days of our Lord and his apostles. read more