Water Came Out Of The Rock Despite Disobedience

There was no water for the community, so they assembled against Moses and Aaron. The people quarrelled with Moses and said, "If only we had perished when our brothers perished before the Lord. Why have you brought the Lord's assembly into this wilderness for us and our livestock to die here? Why have you led us up from Egypt to bring us to this evil place? It's not a place of grain, figs, vines, and pomegranates, and there is no water to drink!"
Then Moses and Aaron went from the presence of the assembly to the doorway of the tent of meeting. They fell facedown, and the glory of the Lord appeared to them. The Lord spoke to Moses, "Take the staff and assemble the community. You and your brother Aaron are to speak to the rock while they watch, and it will yield its water. You will bring out water for them from the rock and provide drink for the community and their livestock."
So Moses took the staff from the Lord's presence just as he had commanded him. Moses and Aaron summoned the assembly in front of the rock, and Moses said to them, "Listen, you rebels! Must we bring water out of this rock for you?" Then Moses raised his hand and struck the rock twice with his staff, so that abundant water gushed out, and the community and their livestock drank.
But the Lord said to Moses and Aaron, "Because you did not trust me to demonstrate my holiness in the sight of the Israelites, you will not bring this assembly into the land I have given them." (Numbers 20:8-12 CSV)

God had asked Moses to speak to the rock but Moses struck the rock twice. Please take note of two things:

1. God's severity toward Moses and he was punished for striking the rock twice;
2. God's kindness to the Israelites and brought water out of the rock despite their unbelief.

Thus the mercy (which is injustice) of God often confuse people when their evil deeds bring prosperity instead of punishment.

Because the sentence against an evil deed is not executed speedily, the heart of the children of man is fully set to do evil. (Ecclesiastes 8:11 ESV)

Note then the kindness and the severity of God: severity toward those who have fallen, but God's kindness to you, provided you continue in his kindness. Otherwise you too will be cut off. (Romans 11:22 ESV)

The Lord is not slow to fulfil his promise as some count slowness, but is patient toward you, not wishing that any should perish, but that all should reach repentance. (2 Peter 3:9 ESV)

Moses Struck The Rock Twice

"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." And Moses took the staff from before the Lord, as he commanded him.
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?" 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. (Numbers 20:8-11 ESV)

Moses struck the rock twice when God told him to speak to the rock. Because of that, he cannot lead Israel into the promised land.

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." (Numbers 20:12 ESV)

But earlier on another occasion, God did asked Moses to strike the rock once.

Behold, I will stand before you there on the rock at Horeb, and you shall strike the rock, and water shall come out of it, and the people will drink." And Moses did so, in the sight of the elders of Israel. (Exodus 17:6 ESV)

The rock is only allowed to be struck once.

For the death he died he died to sin, once for all, but the life he lives he lives to God. (Romans 6:10 ESV)

And just as it is appointed for man to die once, and after that comes judgment, so Christ, having been offered once to bear the sins of many, will appear a second time, not to deal with sin but to save those who are eagerly waiting for him. (Hebrews 9:27-28 ESV)

For Christ also suffered once for sins, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive in the Spirit. (1 Peter 3:18 NIV)

Because the rock was Christ and He died once for our sins.

I would not want you to be unaware that all our fathers were under the cloud, and all passed through the sea, and all were baptized into Moses in the cloud and in the sea; all ate the same spiritual food; and all drank the same spiritual drink, for they drank of that spiritual Rock that followed them, and that Rock was Christ. (1 Corinthians 10:1-4 MEV)

Think I got this verse and the idea that rock was Christ from some YouTube sermon by Adrian Rogers but I have forgotten which sermon.