That they may believe that the LORD God of their fathers, the God of Abraham, the God of Isaac, and the God of Jacob, hath appeared unto thee.
Moses needed this power not once but repeatedly, to prove himself a true Prophet to the Israelites and to silence Pharaoh's presumption. The miracle served two purposes: it strengthened Moses's own faith, but chiefly it compelled the incredulous Israelites to believe and submit to his teaching.
AI summary
Moses objects that the people will not believe him, yet God had promised they would hearken. His doubt does not square with God's word; past rejection made him fear the same again, though he was happily mistaken. The signs God appointed would convince them where bare word could not.
AI summary
Commenting on Exodus 4:1-9
This miracle was not for Moses's faith, the burning bush had already settled that, but for the elders and people of Israel. They needed proof of his divine mission, since his own confidence in God's word was not enough to move them.
AI summary