Exodus 3:12 in the King James Version
And he said, Certainly I will be with thee; and this shall be a 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.
Context
11 Moses said to God, “Who am I, that I should go to Pharaoh, and that I should bring the children of Israel out of Egypt?”
12 He said, “Certainly I will be with you. This will be the token to you, that I have sent you: when you have brought the people out of Egypt, you shall serve God on this mountain.”
13 Moses said to God, “Behold, when I come to the children of Israel, and tell them, ‘The God of your fathers has sent me to you,’ and they ask me, ‘What is his name?’ what should I tell them?”