Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Exo 4:1-9) God gives Moses power to work miracles.
(Exo 4:10-17) Moses is loth to be sent, Aaron is to assist him.
(Exo 4:18-23) Moses leaves Midian, God's message to Pharaoh.
(Exo 4:24-31) God's displeasure against Moses, Aaron meets him, The people believe them.
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.
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.
After God had appeared in the bush, he often spake to Moses. Pharaoh had hardened his own heart against the groans and cries of the oppressed Israelites; and now God, in the way of righteous judgment, hardens his heart against the teaching of the miracles, and the terror of the plagues. But whether Pharaoh will hear, or whether he will forbear, Moses must tell him, Thus saith the Lord. He must demand a discharge for Israel, Let my son go; not only my servant, whom thou hast no right to detain, but my son. It is my son that serves me, and therefore must be spared, must be pleaded for. In case of refusal I will slay thy son, even thy first-born. As men deal with God's people, let them expect so to be dealt with.
God met Moses in anger. The Lord threatened him with death or sent sickness upon him, as the punishment of his having neglected to circumcise his son. When God discovers to us what is amiss in our lives, we must give all diligence to amend it speedily. This is the voice of every rod; it calls us to return to Him that smites us. God sent Aaron to meet Moses. The more they saw of God's bringing them together, the more pleasant their interview was. The elders of Israel met them in faith, and were ready to obey them. It often happens, that less difficulty is found than was expected, in such undertakings as are according to the will of God, and for his glory. Let us but arise and try at our proper work, the Lord will be with us and prosper us. If Israel welcomed the tidings of their deliverance, and worshipped the Lord, how should we welcome the glad tidings of redemption, embrace it in faith, and adore the Redeemer!