In the fourth chapter of Shemonah Perakim (Eight Chapters) Maimonides claimed that Moses committed two transgressions in striking the rock: one - loosing his temper, and the other - causing the people to think mistakenly that the Lord was angry at them for asking for water to drink, and consequently leading the people to think that the Lord is cruel.

Nahmanides strongly disagreed with Maimonides, suggesting instead an interpretation of Rabbenu Hananel:

The closest thing that has been said in this regard, also best for rebutting questions, is the explanation by Rabbenu Hananel, who wrote that the sin was in their saying (Num. 20:10), "Shall we get water for you out of this rock?" when what they should have said was: The Lord will get water out for you! Likewise, all the miracles were to inform them that the Lord was marvelously with them. Perhaps the people thought that Moses and Aaron, in their wisdom, got water for them out of the rock, and that is the meaning of Deuteronomy 32:51: "failing to uphold My sanctity among the Israelite people."

Nahmanides, who sided with Rabbenu Hananel's interpretation, took the stand that a human being is not capable of performing miraculous acts on his own, only as an agent of G-d. Moses and Aaron might have misled the people by their words into thinking that the two leaders were capable of getting water out of a rock and therefore in place of G-d, as it were.

This idea is expressed in the Song of the Well, which appears towards the end of this week's reading (Num. 21:16-18):[1]

And from there to Beer, which is the well where the Lord said to Moses, "Assemble the people that I may give them water." Then Israel sang the song:

Spring up, O well - sing to it -

The well which the chieftains dug,

Which the nobles of the people started

With maces, with their own staffs.

And from Midbar to Mattanah.

In Issaco Samuel Reggio's Torat ha-Elohim[2] this song is interpreted as follows:

It is the way of the world for servants to dig wells, since it requires hard labor. Not so this well, for the chieftains themselves, namely Moses and Aaron, dug it. This is by way of simile, for the words which Moses uttered to the rock (and the blow he struck against it) are likened to digging; for just as by digging in the earth water comes up, so too it came up by Moses' words. It is the way of the world for hewing to be done with an axe and mallets; but no so this well, for hands did not touch it, rather the nobles and leaders of the people hewed it without hard labor, with the staffs in their hands. And mehokek (rendered here as "maces") is the lawgiver, and the mace in the lawgiver's hand symbolizes greatness and honor.

Note that at the beginning of this song (which opens with the words "Spring up") there is no mention whatsoever of the Lord's grace in giving them water, and this is evidence in support of our interpretation of Moses' and Aaron's sin as being that the people believed then that Moses and Aaron, by their own might, had gotten out water for them, and therefore they praised them in this song. Moses, however, having seen that profanation of the Lord had resulted from his actions, took care to say to them in Deuteronomy that this was an act of the Lord, as it is said: "who brought forth water for you from the flinty rock" (Deut. 8:15).

If we accept Reggio's interpretation of the Song of the Well, it substantiates Nahmanides' idea (with which Reggio agreed) about the essence of Moses' and Aaron's sin at the Waters of Meribah. Their sin lay in saying, "Shall we, and not the LORD, get water for you out of this rock." In other words, their sin was in misleading the people regarding the source of the miracle.

In this context we can understand the punishment decreed on Moses and Aaron, that they not enter the land. Their punishment served to prevent confirmation of the error regarding their status among the people. For, if Moses and Aaron were to accompany the people in conquering and settling the land - an era characterized, among other things, by miracles that were done for Israel (such as crossing the Jordan, capturing Jericho, the miracles at Gibeon and the Valley of Ayalon, etc.), the mistake in ascribing these miracles to them might have become deeply rooted among the people. Leaders, for all their greatness, do not transcend the limitations of human beings.

[1] Most commentators believe that these verses describe the deed in reference to the famous sin of Moses and Aaron at the Waters of Meribah (above, 10:7-11), but Da'at Mikra on this verse holds that the Torah is alluding here to another miracle that was performed for Israel and was well-known among the people, rather than the miracle of striking the rock, which happened far away from the eastern borders of Moab, where the people were presently located.

[2] Isacco Samuel Reggio, 1784-1855, Italian rabbi, associated with Hokhmat Yisrael, and founder of Collegio Rabbinico Italiano in Padua.