Comentario sobre Números 20:11

פעמים [HE SMOTE THE ROCK] TWICE, because at the first attempt it did not bring forth more than a few drops, for God had not bidden him smite it, but He had said, (v. 8) “and ye shall speak to the rock”. They had, indeed, spoken, but to a different rock (not that which God had intended) and it had not given forth water. They said, “Perhaps it is necessary to smite it as on the former occasion when it says, (Exodus 17:6) ‘and ye shall smite the rock’, and just that rock intended by God happened to be there and they smote it [but without full effect, and so they smote it a second time] (cf. Midrash Tanchuma, Chukat 9).

במטהו פעמים with his staff, twice. The reason he hit the rock twice was similar to a servant who is eager to carry out his master's instructions. Our sages in Sanhedrin 34 use this verse to illustrate the principle that a single verse yields many diverse insights.

Because at first … only drops. Rashi is answering the question: Why did he strike it twice? He answers that this was because after striking it once it only produced drops. His proof is that if it had not produced anything, why would he have stuck it a second time? Also, why would he not have thought that it was a different rock, about which Hashem had not commanded them? Conversely, if at first it had produced abundant water, they would not have had to strike it a second time. Rather, it is certain that at first it produced drops and therefore he struck it a second time. The reason why it did not produce sufficient water immediately was “Because [the Omnipresent] had not…” Rashi adds “They spoke…” so that Moshe’s mistake be known, that he struck it. Because they had spoken to a different rock and it had not produced water. Consequently he struck the rock, because they said, “Perhaps…” Rashi adds that they happened upon [that rock] because if this were not so, why would it have even produced drops? Even after many strikes it should not have produced even one drop of water! Rather, “They happened upon [that rock]…” There is a minor difficulty based on Rashi’s explanation in Parshas Matos concerning the verse (Bamidbar 31:21) “Elozor the Kohein said…” [There he states]: “Because Moshe fell into a state of anger he fell into a state of error… similar to ‘listen now rebels… he struck the rock’ and because of anger he came to a state of error.” This implies that it was not because they had spoken to another rock and it had not produced water, and that they thought perhaps Hashem’s command was to strike it, like Rashi writes here. The answer may be that these are Midrashim that disagree with each other and Rashi brings both, as is his practice. Re’m.

ויך את הסלע, “he struck the rock with his staff twice.” Rashi’s explanation here is too short when he writes that after the first strike the rock produced only a few drops of water, Moses struck the rock again and then it produced ample amounts of water because G-d had never instructed him to hit the rock at all, but had said to Moses and Aaron: “speak to the rock.” According to Rashi, they then spoke to another rock. The result was that no water emerged from that rock at all. They then thought that this second rock should have been struck just like the first one, and when they proceeded to do this a lot of water came out. When the rock had failed to produce water, they had thought that they must have spoken to the wrong rock. (Our author amends what he thought that Rashi had meant to write)