Charles Spurgeon Commentary Exodus 3:12

"And he said, Certainly I will be with thee; and this shall be the token unto thee, that I have sent thee: when thou hast brought forth the people out of Egypt, ye shall serve God upon this mountain." — Exodus 3:12 (ASV)

And he said, Certainly I will be with thee;

What more does Moses want? He said, "Who am I?" This showed his weakness. God said, "Never mind who you are.

Certainly I will be with thee." Here was strength enough for him.

And this shall be a token to you, that I have sent you: When you have brought forth the people out of Egypt, you shall serve God upon this mountain.

And he did. You know how Sinai trembled while God made it his throne, and how Moses must have been strengthened when he exceedingly feared and quaked before God, when he recollected that this same God had appeared to him when he was alone in the desert and had promised that they should worship him there.