Ex 7:17

7:17 The use of the rod with the first three and the last three plagues shows that Yahweh is the real author.

I will strike. Aaron will strike (vv. 19, 20), but the Lord will perform the miracle. The striking is by God’s hand, by His rod. The deed of Aaron is owned by God no less than the word that God gave him through Moses.

blood. In Hebrew the word never denotes its red color, but always blood as a substance. The red clay that comes down at the time of flooding from the Ethiopian highlands (coloring the Nile water) is not in view.