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.
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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.

“Grant me, O Lord” prayed Lancelot Andrewes, “for nothing earthly, temporal or mortal to long or to wait.”

In Exodus 16 the people long for the fleshpots of Egypt.

The Lord provides supernaturally. Manna is natural nourishment, but supernaturally provided and supernaturally administered. It shows up on the rainless desert floor every morning, like dew. They gather what they need, one omer to each person. One omer is sufficient for a child or a growing teenager, apparently. Nobody lacks, nobody goes hungry, it is the perfect food.

On the sixth day they gather twice at much. There must have been twice as much there to gather, because they wonder about it; they come and ask Moses. He says it is what the Lord had said, which he did. It’s just they know that if they keep it from one day to the other, it usually hasn’t lasted. But on this occasion they are supposed to keep it for the next day. There’s going to be a day of rest.

Knowing that every other day manna doesn’t last from one day to the other, there is only God’s word for it that one day out of seven it will behave otherwise. Of course, it is miraculously supplied, and it is strangely sufficient in the advised quantity of an omer. Everything about this natural food is unusual.

Of course there are those who keep it and find out about the nasty side of manna, as well as those who go out looking on the Sabbath. Both are disappointed. Both failed the test, because God says he set it up to test them. “Then the LORD said to Moses, “Behold, I am about to rain bread from heaven for you, and the people shall go out and gather a day’s portion every day, that I may test them, whether they will walk in my law or not.”

Why did he have to test them?

When God made the world he set up a similar test: a tree of the knowledge of good and evil, and similarly offered all the rest of the garden to humanity, forbidding only one tree’s fruit. All of creation was good, at that point: very good. But the question is, good for what?

Good for testing. What did Eve do? She saw that it was desirable to make one wise. She longed for that which was temporal, earthly, and deadly mortal.

God tested his people in the wilderness. He heard their grumbling, and before he acted it tells us that Moses and Aaron gathered the people: “And as soon as Aaron spoke to the whole congregation of the people of Israel, they looked toward the wilderness, and behold, the glory of the LORD appeared in the cloud.”

Why?

Why do they look now?

Why do all of them turn their heads away at the same moment, looking toward the wilderness?

Why does God surprise them now when he has promised to show them his glory in the morning?

Because God was looking in them for a desire for that which is not earthly, temporal, and mortal. It is a desire for one who will not just nourish earthly, temporal, and mortal life. “Jesus then said to them, ‘Truly, truly, I say to you, it was not Moses who gave you the bread from heaven, but my Father gives you the true bread from heaven. For the bread of God is he who comes down from heaven and gives life to the world.’”
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They look toward the wilderness, toward the cloud that has and is guiding them, toward the destination which is the glory of the Lord himself, his presence, and the final rest. God knows what they need. He gives the Sabbath so that they will hold back from those things which are merely earthly, temporal, and mortal and cultivate a longing for what is heavenly, eternal, and immortal. He knows what we need, and he gives us Jesus Christ, the bread from heaven, and the one in whom the weary rest. 

The end of the chapter has a short story about the bitter waters of Marah. The people head for the wilderness of the wall—perhaps some Egyptian border fortification. When they’re running out of water, they come on water they cannot drink. Bitter, bitter, bitter, bitter, you read in Hebrew, which seems to be an implied superlative. Do they feel mocked by the circumstances? They murmur.

Of all the things there are to find in the wilderness, the Lord shows Moses a tree. Wood and water is how the plagues on Egypt began; Aaron took the rod and struck the Nile, and as a result the Egyptians had to dig around for water. This is why the Lord says he will put none of the disease on them that he put in the Egyptians. He does the reverse, he makes the water potable.

And it is a warning, so that nobody thinks that God chose Israel because they were slightly better than the Egyptians, that they were less likely to oppress other people the way the Egyptians oppressed them. If you think back to the time of Abraham and Sarah, you will remember Hagar the Egyptian slave. God is saying to the people here in Exodus 15 that they are no better than any others, that none who are chosen are better, but they are chosen because he is the Lord their healer. Unlike Pharaoh, there is mercy with the Lord.

Origen of Alexandria, who was tortured for his faith and refused to deny the Lord, speaks of how the wood of the Gospel makes the bitter waters of the law sweet. Isn’t that a good picture of the way it ought to work? Who loves the law thinking of it merely as a series of prohibitions? Who says, O how I love thy law as something that simply forbids and restricts and curtails? But when the law is a revelation of God’s character, when we understand that God when he forbids adultery does it because he is faithful, because he loves faithfulness, because he is faithful even to the unfaithful, because he is telling us about Christ, then we taste the sweetness of those waters.
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Of all the things to show up in a wilderness, not a bush, not a bleached skull, not a cactus or a tumbleweed, but a tree. Sometimes a tree is just a tree. Still, is it any coincidence when everything wrong with the human race beings at a tree, and everything restored again takes place at a tree, that what Moses sees when he cries out to the Lord in the wilderness is a tree?