9 And if they have no faith even in these two signs and will not give ear to your voice, then you are to take the water of the Nile and put it on the dry land: and the water you take out of the river will become blood on the dry land.

Matthew Henry's Commentary on Exodus 4:9

Commentary on Exodus 4:1-9

(Read Exodus 4:1-9)

Moses objects, that the people would not take his word, unless he showed them some sign. God gives him power to work miracles. But those who are now employed to deliver God's messages to men, need not the power to work miracles: their character and their doctrines are to be tried by that word of God to which they appeal. These miracles especially referred to the miracles of the Lord Jesus Christ. It belonged to Him only, to cast the power of the devil out of the soul, and to heal the soul of the leprosy of sin; and so it was for Him first to cast the devil out of the body, and to heal the leprosy of the body.