Charles Ellicott Commentary Exodus 7:25

"And seven days were fulfilled, after that Jehovah had smitten the river." — Exodus 7:25 (ASV)

And seven days were fulfilled. —These words seem to mark the duration of the first plague, which was longer because Pharaoh made no submission at all as a result of it. Obtaining sufficient water for his own purposes (see the comment on Exodus 7:23), he thought little of its continuance.