One way to preach Christ from the OT is to analogy or parallel uses in the NT for which one text becomes a commentary or example. Here is one set of parallel texts which, when set in conjunction, help to elucidate the other. Numbers 20 tells the story of the Israelites complaining in the wilderness. It is common to look upon these grumblers and mock them; or to wonder at how anyone could be as fickle as they were.
It is a strange glimpse into the 40 years of wilderness walking. Aside from the miracle of the water from the rock, one may even wonder at the point. There is also the strange ending about The Lord proving himself holy:
2 Now there was no water for the congregation. And they assembled themselves together against Moses and against Aaron. 3 And the people quarreled with Moses and said, “Would that we had perished when our brothers perished before the LORD! 4 Why have you brought the assembly of the LORD into this wilderness, that we should die here, both we and our cattle? 5 And why have you made us come up out of Egypt to bring us to this evil place? It is no place for grain or figs or vines or pomegranates, and there is no water to drink.”
6 Then Moses and Aaron went from the presence of the assembly to the entrance of the tent of meeting and fell on their faces. And the glory of the LORD appeared to them, 7 and the LORD spoke to Moses, saying, 8 “Take the staff, and assemble the congregation, you and Aaron your brother, and tell the rock before their eyes to yield its water. So you shall bring water out of the rock for them and give drink to the congregation and their cattle.” 9 And Moses took the staff from before the LORD, as he commanded him.10 Then Moses and Aaron gathered the assembly together before the rock, and he said to them, “Hear now, you rebels: shall we bring water for you out of this rock?”
11 And Moses lifted up his hand and struck the rock with his staff twice, and water came out abundantly, and the congregation drank, and their livestock.12 And the LORD said to Moses and Aaron, “Because you did not believe in me, to uphold me as holy in the eyes of the people of Israel, therefore you shall not bring this assembly into the land that I have given them.”13 These are the waters of Meribah, where the people of Israel quarreled with the LORD, and through them he showed himself holy.
When one considers the scene, the Israelites don’t seem all that wretched. They are in the desert, they are thirsty. And, they remember that in Egypt, when lived like other people, they had enough of what they needed. Why is God angry? “Because you did not believe in me.” (v. 12)
Now compare this with Romans 12, a text which Christians are fond of quoting:
1 I appeal to you therefore, brothers, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship.
2 Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect.
3 For by the grace given to me I say to everyone among you not to think of himself more highly than he ought to think, but to think with sober judgment, each according to the measure of faith that God has assigned.
Now bring the two texts together and see what sort points are raised. Could we say that the Israelites were being conformed to this world? Did they think of themselves rightly? Is there a way in which I am conformed in my complaints? How is God holy in all of this? Is God right in the measure of faith he has assigned to me? I am not answering any of these questions. Rather, they are the sort of questions which strike me as I read one passage after the other.