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 17:5

17:5 The Lord said to Moses, “Go over before the people; take with you some of the elders of Israel and take in your hand your staff with which you struck the Nile and go.