Exodus 7:14-24

14 Then the LORD said unto Moses, Pharaoh’s heart is become grievous, for he refuses to let the people go.
15 Go unto Pharaoh in the morning; behold, he goes out unto the water; and thou shalt stand by the river’s brink before him and take in thy hand the rod which was turned to a serpent
16 and say unto him, The LORD, the God of the Hebrews has sent me unto thee, saying, Let my people go, that they may serve me in the wilderness; and, behold, until now thou hast not desired to hear.
17 Thus hath the LORD said, In this thou shalt know that I am the LORD; behold, I will smite with the rod that is in my hand the waters which are in the river, and they shall be turned to blood.
18 And the fish that are in the river shall die, and the river shall stink; and the Egyptians shall loathe to drink the water of the river.
19 And the LORD spoke unto Moses, Say unto Aaron, Take thy rod and stretch out thine hand upon the waters of Egypt, upon their rivers, upon their streams, and upon their ponds, and upon all their pools of water, that they may become blood and that there may be blood throughout all the land of Egypt, both in vessels of wood and in vessels of stone.
20 And Moses and Aaron did so, as the LORD commanded; and lifting up the rod, he smote the waters that were in the river, in the sight of Pharaoh and in the sight of his slaves; and all the waters that were in the river were turned to blood.
21 And the fish that were in the river died; and the river became corrupted, so that the Egyptians could not drink the water of the river; and there was blood throughout all the land of Egypt.
22 And the magicians of Egypt did the same with their enchantments; and Pharaoh’s heart hardened itself, and he did not hearken unto them, as the LORD had said.
23 And Pharaoh turned and returned to his house, and even with all this he did not take this to heart.
24 And in all Egypt they dug wells round about the river for water to drink, for they could not drink of the water of the river.