Numbers 20:8

And their livestock. From here [we derive] that the Holy One, Blessed is He, is solicitous of the Israelites’ property.

Take the rod of the miracles, and gather the congregation, thou, and Aharon thy brother, and both of you adjure the rock, by the Great and manifested Name, while they look on, and it shall give forth its waters: but if it refuse to bring forth, smite thou it once with the rod that is in thy hand, and thou wilt bring out water for them from the rock, that the congregation and their cattle may drink.

The sin of Moses and Aaron in the [matter of the] waters of Meribah is not clearly expressed in Scripture. Rashi explains that [their sin consisted of hitting the rock], because He had commanded them, and speak ye unto the rock, and did not say “and ye shall strike it.” For had they spoken [to the rock and it had brought forth water] the Holy One, blessed be He, would have been sanctified before the whole congregation, since the people would have said: “If [even] this rock, which does not hear and does not speak, nonetheless obeys the command of the Holy One, blessed be He, how much more so should we [obey His commands]!” These words are [in the nature of] a homiletic interpretation, but they do not clarify [the matter]. For since G-d had commanded Moses: Take the rod, it implied that he should smite [the rock] with it, for had He only wanted that he should speak to it, what was [the point of] this rod in his hand? Similarly, in the [case of the] plagues of Egypt where He said, and the rod which was turned to a serpent shalt thou take in thy hand it was in order to smite with it;, Verse 17: I will smite with the rod that is in my hand upon the waters which are in the river. and sometimes He said, Stretch forth thy hand [with thy rod],, 8:1. when the meaning is: “to smite with the rod,” since Scripture writes briefly when the subject-matter is self-understood. Moreover, the miracle [involved in the rock giving forth water] is no greater if [accomplished] by speech than by smiting, for as far as the rock is concerned both are equal. Furthermore [if the sin consisted of smiting the rock], why did He say about this: ye [Moses and Aaron] trespassed against Me? [It cannot be because they failed to speak to the rock], for the [fulfillment of the] command to [Moses to] speak to the rock is indeed [also] mentioned at the occurrence [of the event]! Thus He commanded [Moses and Aaron] to say whilst the rock “listens” that G-d will bring forth water out of this rock, similar to [that which Joshua said about a stone which he put up as a witness to the covenant which he made with the people], for ‘it hath heard’ all the words of the Eternal. And they [Moses and Aaron] indeed did so, as Scripture states, And Moses and Aaron gathered the assembly together before the rock, and he said unto them etc. Thus the rock did “hear” when he [Moses] spoke these words to all the …

קח את המטה, which at that time was reposing next to the Tablets. (compare Numbers 17,25)

ודברתם אל הסלע, G’d did not command Moses to take the staff in order to strike the rock as he had commanded him in Exodus 17,6. He only commanded Moses to display the staff to remind them that they had again been very obstinate. They had acquired this attribute in Numbers 17,25 when the Torah speaks of למשמרת לאות לבני מרי, “to be kept as a lesson to rebels.” However, the water was to be produced merely by speaking to the rock.

והוצאת להם מים, by means of your speaking to the rock.

קח את המטה...ודברתם אל הסלע, there are numerous opinions of what precisely Moses’ sin consisted of. Many commentators have difficulty understanding the wordsלא האמנתם, ‘you lacked faith” in verse 12 as well as with the word מעלתם בי, “you trespassed against Me” in Deuteronomy 32,51, as well as the words מריתם את פי “you rebelled against My command” in verse 24 of our chapter here.
If it had indeed been G’d’s intention that they were only to speak to the rock, what purpose was served in commanding Moses to take the staff? If the sin consisted in that Moses struck the rock, something he had not been commanded to do, what was Aaron’s sin?
However, when we scrutinise the matter (the quarrel) more thoroughly we must remember that G’d’s instructions were designed to bring home to the people how wrong they had been in their rebellious attitude. They were meant not only to become aware of this, but to repent it and to apologise for it, seeing that G’d does not desire the death of the sinner but his rehabilitation by his own efforts.
Knowing that this is so, Moses and Aaron’s actions or inaction resulted in G’d’s intention of bringing about the people’s repentance of their conduct was thwarted. G’d punished them for having become the instrument of thwarting His plan.
The quarrel of the people with Moses was that they accused him of a failure of leadership that resulted in their finding themselves in a situation where they even lacked water for survival. Their quarrel with G’d consisted in their accusing Him of taking them out of a good land called Egypt and bringing them to a desert instead. G’d had wanted to make it clear to them by means of the miracle that Moses had not acted on their own but had merely been His messenger, had carried out his mission faithfully, and that the One Who had sent him had not caused the people any harm at all. We must remember that there are three distinct kinds of miracles in Scripture
1) The “hidden” miracle such as that rain occurs when needed, or that people are recovering from a variety of life threatening diseases. These are the types of miracles that the righteous can bring about by means of their prayers. The Torah quotes an example of this kind of miracle in Genesis 20,17 when it tells us that Avraham’s prayer resulted in G’d healing the households in Avimelech’s kingdom where an outbreak of a disease had resulted in none of the expectant women being able to give birth to their babies until after …

קח את המטה והקהל את העדה, “take the staff and assemble the congregation!” According to Rabbi b’chor shor, the instruction to Moses to take the staff was meant in order for him to strike the rock with it which was meant to produce the water. [The instructions addressed to both Moses and Aaron in the same verse, were addressed to both Moses and Aaron who were to speak to the people first Ed.] This was similar to the instructions in Exodus 17,6, except that there the rock was called צור, tzur. At that time G–d was going to provide both bread (heavenly), meat, (quails) and water, each one of which was listed in detail shortly thereafter. The provision of water on both occasions is to be understood as the same miracle, and that is also why the first location was called מסה ומריבה, “trying and strife,” and on this occasion reference is only made to מי מריבה, “waters of strife” (verse 13) When Moses, in retrospect, refers to these events in Deuteronomy 33,8 he uses both expressions in the same verse. They are referred to also in Numbers 20,24:למי מריבה ”at the waters of strife.” Those waters were in the desert of Sin, near Mount Sinai, (during the first year of the Exodus) As far as the instructions here for Moses and Aaron to address the rock by word of mouth, ודברתם אל הסלע, is concerned, they were meant to speak to the people near the rock in order to watch the miracle about to be performed. On the first occasion, Moses took the elders with him, but the people stayed far behind and they did not even witness the striking of the rock. Those elders had long died so that the present generation had not even been told what they had witnessed. (Exodus 17,5) The water at that time formed into a small river and that was where the Israelites filled their buckets from. Moses and Aaron, instead of announcing the miracle about to take place, addressed the people by calling them rebellious, and asking if they really expected that they were worthy of G–d performing such a miracle for them. They should have known that it was not in Moses’ or Aaron’s power to get water out of a stone, so what was the point of accusing them of the shortage of water. Therefore, they should have prayed to G–d in a deferential manner, asking Him to help them in their predicament. If Moses and Aaron had explained all this to them without displaying anger with a thirsty people, the result would have been a great sanctification of the Lord’s name. According to the plain meaning of the text, Moses’ and Aaron’s sin consisted of using the word נוציא לכם מים, “We are going to produce water for you,” instead of saying that “G–d is going to produce water for you.”