Albert Barnes Commentary Exodus 4:1

"And Moses answered and said, But, behold, they will not believe me, nor hearken unto my voice; for they will say, Jehovah hath not appeared unto thee." — Exodus 4:1 (ASV)

With this chapter begins the series of miracles which resulted in the deliverance of Israel. The first miracle was performed to remove the first obstacle, namely, the reluctance of Moses, conscious of his own weakness, and of the enormous power with which he would have to contend.