Why did Hashem order Moshe to "pass before the people"?
Rashi: To show him that they would not stone him, as he claimed they would.
Ramban: Because, since the people were stationed in Refidim, whereas the rock was situated in Chorev, 1 in which case he had to pass before the people in order to reach it.
Seforno: So that, when they saw him making efforts on their behalf, they would stop complaining.
Ramban: Which is either alias Har Sinai (see Shabbos 89b), or a town close to that mountain.
Why did Hashem instruct Moshe to take some of the elders with him?
Rashi: To testify that he had produced water from the rock, so that the people should not claim that there had been ancient fountains there.
Why did Hashem instruct Moshe to take with him the staff with which he had struck the River Nile?
Rashi: Because the people were claiming that the staff was only good for punishments; 1 now they would witness how it was capable of doing good as well.
Ramban and Seforno: To show that the staff was able to perform opposite functions - In Egypt, it prevented the Egyptians from drinking; whereas here it enabled the people to drink. 2
What was the significance of Moshe's staff?
Refer to Shemos 4:17:1 and 4:17:2.1 .
Where was Moshe supposed to go?
Ramban: He was to take some of the elders and his staff with him; and go to the rock at Chorev, 1 where he would find Hashem waiting for him. 2
Targum Yonasan: ' ... and go away from their complaints (i.e., take your mind off of them 3 - Yayin ha'Tov).
Although the Pasuk does not record that "the congregation and their animals drank" (as it will do later in Parshas Chukas, see Bamidbar 20:11), it is obvious that they did so now as well (Ramban). Where did they drink it?
Ramban #1: Clearly, they did not arrive at Har Sinai (Chorev) before the first of Sivan (see 19:1-2). Consequently, they could not have gone to the rock to drink. They must therefore have sent their young men with their animals to fill pitchers with water, and brought these back to the camp.
Ramban #2: The water that emerged from the rock after Moshe struck it, was cool flowing water - which miraculously flowed all the way to Refidim, 1 where the people collected and drank it.
Ramban: Where, throughout the forty years (until the second episode), rivers flowed from it, from which the people drew water and drank.
Seeing as it was Aharon who struck the river in Egypt, why does Hashem say "u'Matecha Asher Hikisa Bo Es ha'Ye'or" - addressing Moshe?
Moshav Zekenim (in 14:7) #1: Because 'one's Shali'ach is like oneself.'
Moshav Zekenim (in 14:7) #2: Because although Aharon struck the river, Moshe raised the staff.
Sanhedrin 99b: This teaches us that when someone makes his friend perform a Mitzvah, it is as if he himself had performed it. 1
And it was Moshe who ordered Aharon to strike the river. See also Torah Temimah, note 4.