Exodus 4:1 And Moses answered and said, But, Behold, they will not believe me, nor hearken unto my voice: for they will say, The Lord hath not appeared unto thee.
Naturally, why should anyone believe a man who says, ”God told me?” It certainly would be hard to believe anyone who had been in the desert for 40 years and then came back with incredible news. This was a sincere objection on Moses’ part: Why should they believe me?
But the unbelief of Moses also shows up up here, for in 3:18 God said, ”And they will hearken to thy voice.” Moses plainly contradicts God’s Word: ”They will not listen.” Moses heard directly from the Lord in a personal encounter, yet he couldn’t fully trust the Word. The devil tempted Adam and Eve to doubt God’s Word, and she gave in. The devil tempted Jesus to doubt and He did not give in. Instead, He used God’s Word in faith to overcome him. Jesus did that for us, and He gave us His victory.
The same unbelievable and impossible Truth of deliverance and salvation has come to us in the Gospel. Through the gospel the Spirit gives us the faith to believe it. Like the people, I cannot by my own reason or strength believe, but HS calls.
God proceeded to give Moses signs and wonders to aid belief: rod becoming a serpent and hand becoming leprous. God gives us signs in Gospel and Sacraments to strengthen our faith. We respond by hearkening to the Lord.