Exodus 4:9

4:9 And if they do not believe even these two signs or listen to you, then take some water from the Nile and pour it out on the dry ground. The water you take out of the Nile will become blood on the dry ground.”

Exodus 7:20

7:20 Moses and Aaron did so, just as the Lord had commanded. Moses raised the staff and struck the water that was in the Nile right before the eyes of Pharaoh and his servants, and all the water that was in the Nile was turned to blood.