8 The Lord said to Moses, "If they do not believe you and are not convinced by the first miraculous sign, they will be convinced by the second sign. 9 And if they don't believe you or listen to you even after these two signs, then take some water from the Nile River and pour it out on the dry ground. When you do, the water from the Nile will turn to blood on the ground."

10 But Moses pleaded with the Lord, "O Lord, I'm not very good with words. I never have been, and I'm not now, even though you have spoken to me. I get tongue-tied, and my words get tangled." 11 Then the Lord asked Moses, "Who makes a person's mouth? Who decides whether people speak or do not speak, hear or do not hear, see or do not see? Is it not I, the Lord ? 12 Now go! I will be with you as you speak, and I will instruct you in what to say." 13 But Moses again pleaded, "Lord, please! Send anyone else."

Matthew Henry's Commentary on Exodus 4:8-13

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.

Commentary on Exodus 4:10-17

(Read Exodus 4:10-17)

Moses continued backward to the work God designed him for; there was much of cowardice, slothfulness, and unbelief in him. We must not judge of men by the readiness of their discourse. A great deal of wisdom and true worth may be with a slow tongue. God sometimes makes choice of those as his messengers, who have the least of the advantages of art or nature, that his grace in them may appear the more glorious. Christ's disciples were no orators, till the Holy Spirit made them such. God condescends to answer the excuse of Moses. Even self-diffidence, when it hinders us from duty, or clogs us in duty, is very displeasing to the Lord. But while we blame Moses for shrinking from this dangerous service, let us ask our own hearts if we are not neglecting duties more easy, and less perilous. The tongue of Aaron, with the head and heart of Moses, would make one completely fit for this errand. God promises, I will be with thy mouth, and with his mouth. Even Aaron, who could speak well, yet could not speak to purpose, unless God gave constant teaching and help; for without the constant aid of Divine grace, the best gifts will fail.