Exodus 7:17

13 Still, Pharaoh’s heart was hardened, and he would not listen to them, just as the LORD had said.

14 Then the LORD said to Moses, “Pharaoh’s heart is unyielding; he refuses to let the people go.

15 Go to Pharaoh in the morning as you see him walking out to the water. Wait on the bank of the Nile to meet him, and take in your hand the staff that was changed into a snake.

16 Then say to him, ‘The LORD, the God of the Hebrews, has sent me to tell you: Let My people go, so that they may worship Me in the wilderness. But you have not listened until now.

17 This is what the LORD says: By this you will know that I am the LORD. Behold, with the staff in my hand I will strike the water of the Nile, and it will turn to blood.

18 The fish in the Nile will die, the river will stink, and the Egyptians will be unable to drink its water.’”

19 And the LORD said to Moses, “Tell Aaron, ‘Take your staff and stretch out your hand over the waters of Egypt—over their rivers and canals and ponds and reservoirs—that they may become blood.’ There will be blood throughout the land of Egypt, even in the vessels of wood and stone.”

20 Moses and Aaron did just as the LORD had commanded; in the presence of Pharaoh and his officials, Aaron raised the staff and struck the water of the Nile, and all the water was turned to blood.

21 The fish in the Nile died, and the river smelled so bad that the Egyptians could not drink its water. And there was blood throughout the land of Egypt.

Read all of Exodus 7