But I will be with you, and this shall be the sign for you, that I have sent you: when you have brought the people out of Egypt, you shall serve God on this mountain.Bear in mind - Moses is seeking some reassurance here. A sign is probably what he is expecting. But this is problematic. The sign offered will only be seen after Moses has ventured everything, risked his life and the lives of his people in a confrontation with Pharaoh. Moses will know God has sent him when he sees the outcome of his actions.
Two interesting things about that. Firstly, Moses has already seen a sign - the burning bush itself. But it seems that was just to get his attention. Is that the way God normally uses signs? Is that the way the more spectacular charismata in the church are meant to work?
Secondly, Moses has to set out in faith, trusting in God's word. He has to step out onto God's promise, trusting that that promise will take his weight, and only as he does so will he brought to the place where he will see (rather than believe) that God is with him. Of course, he gets more signs after that, but they are given to him in response to his unbelief. The narrative makes it clear that he should have just taken God at his word.
What does that mean for my response to the word of God? What does it mean for the Christian life, walking by faith and (not yet) by sight?