Let's first take a look at the passage where Moses disobeys God
7 And the LORD spake unto Moses, saying,
8 Take the rod, and gather thou the assembly together, thou, and Aaron thy brother, and speak ye unto the rock before their eyes; and it shall give forth his water, and thou shalt bring forth to them water out of the rock: so thou shalt give the congregation and their beasts drink.
9 And Moses took the rod from before the LORD, as he commanded him.
10 And Moses and Aaron gathered the congregation together before the rock, and he said unto them, Hear now, ye rebels; must we fetch you water out of this rock?
11 And Moses lifted up his hand, and with his rod he smote the rock twice: and the water came out abundantly, and the congregation drank, and their beasts also.
12 And the LORD spake unto Moses and Aaron, Because ye believed me not, to sanctify me in the eyes of the children of Israel, therefore ye shall not bring this congregation into the land which I have given them.
We see in this passage that Moses was commanded to speak to the rock that it would bring forth water. But, Moses disobeyed God and struck the rock. At first glance this may not seem to be like much of a big deal but we will discover the spiritual typology within all of this and the reasoning to why God took it so seriously.
Now let's take a look at
1 Corinthians Chapter 10:2-4
2 And were all baptized unto Moses in the cloud and in the sea;
3 And did all eat the same spiritual meat;
4 And did all drink the same spiritual drink: for they drank of that spiritual Rock that followed them: and that Rock was Christ.
So we can see the spiritual typology here. The meat which the Israelites was to represent Jesus Christ
32 Then Jesus said unto them, Verily, verily, I say unto you, Moses gave you not that bread from heaven; but my Father giveth you the true bread from heaven.
33 For the bread of God is he which cometh down from heaven, and giveth life unto the world.
And the water which flowed from the rock was also to represent Christ
But whosoever drinketh of the water that I shall give him shall never thirst; but the water that I shall give him shall be in him a well of water springing up into everlasting life.
So the spiritual typology is obvious. When Moses was commanded to strike the rock the first time it was to represent the death of Jesus.
Behold, I will stand before thee there upon the rock in Horeb; and thou shalt smite the rock, and there shall come water out of it, that the people may drink. And Moses did so in the sight of the elders of Israel.
Jesus Christ was only needed to die ONCE for our sins for ever.
10 By the which will we are sanctified through the offering of the body of Jesus Christ ONCE FOR ALL.
11 And every priest standeth daily ministering and offering oftentimes the same sacrifices, which can never take away sins:
12 But this man, after he had offered one sacrifice for sins for ever, sat down on the right hand of God;
And so when Moses struck the rock the second time and disobeyed God, he completely destroyed the spiritual typology of the rock which represented Jesus Christ. Moses was told to speak to the rock the second time because speaking to it would represent confession of sins to Jesus Christ and salvation.
1 John 1:9
If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.
So Moses disobedience completely destroyed this spiritual typology and this only shows how much importance spiritual typology is to God.