In Exodus 17 there is an insurrection. The formal complaint against Moses becomes alarming. Not only does Moses fear for his life (they’re about to stone me), he also warns them that they are being irreverent in their behavior, they are complaining against the Lord.
It is interesting that they complain to Moses: they do it because they can see him. The passage is about walking by faith and not by sight, and the problem they have is they go by sight and not by faith. Moses is visible to them. God’s presence with them cannot be at this point doubted, but they are obviously not operating on trust. They walk by sight and not by faith, and that is at the heart of this event.
In his response, Moses has to walk by faith and not by sight. Whose idea of a shortage of water is to walk up to a rock and whack it with a stick? The Lord would be there, of course, but does anybody think that when God said he would stand by the rock, that he would be visible there? No, Moses had to walk through the angry crowd, he had to walk before them, go to the front of the encampment, be toward where they were being led by God, gather witnesses for the solemn occasion, and trust that then he hit a rock with his stick, God, who was there, would do something so water would be supplied. He had to walk by faith and not by sight.
That Moses used the rod first found in his hand back when he encountered the burning bush is significant. Take the rod which you used to strike the Nile, God says. It is the rod that took away the Egyptian’s source of water. It is the rod that brought the first plague, and it is the rod used to strike Egypt with all the plagues of God’s judgment. In the last incident with water, at Marah, the Lord also mentioned how he healed his people from their plagues. He supplied water to the underserving, instead of taking it from those who deserve to die. God did not rescue Israel because it was a better nation. That was a lesson about unconditional election; this, at Massah and Meribah, is a lesson about substitutionary atonement.
This is why Paul says that the rock was Christ. Who is struck with the rod bringing all the plagues that God’s people deserve and as a result pours out streams of living water? If you are reading by faith and not by sight, you will understand that the rock was Christ. Someone has to be stricken once for all for the transgressions of his people.