Thus says the Lord: “By this you will know that I am the Lord: I am going to strike ¹  the water of the Nile with the staff that is in my hand, and it will be turned into blood. ² 

So Moses said to Joshua, “Choose some of our ¹  men and go out, fight against Amalek. Tomorrow I will stand on top of the hill with the staff of God in my hand.”