Exodus 7:22-25

Using their tricks, the magicians of Egypt did the same thing. So the king was stubborn and refused to listen to Moses and Aaron, just as the LORD had said. The king turned and went into his palace and ignored what Moses and Aaron had done. The Egyptians could not drink the water from the Nile, so all of them dug along the bank of the river, looking for water to drink. Seven days passed after the LORD changed the Nile River.