9 And it shall come to pass, if they will not believe also those two signs, neither hearken unto thy voice, that thou shalt take of the water of the river, and pour [it] on the dry [land]; and the water that thou takest out of the river shall become blood upon 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.