What is the Torah referring to when it writes "Heimah Mei Merivah ... "?
Rashi: It is referring to the astrologers of Par'oh, who ordered all the babies boys thrown into the Nile, because they saw that the savior of Yisrael would be smitten by water - and they interpreted it to mean that whoever that savior was, he would drown there. 1
Ramban: It is coming to draw a distinction between the current incident, where all of Yisrael were present, and the incident in Refidim, where Moshe only assembled the elders. 2 And the Pasuk sees fit to point out for which of the two Moshe and Aharon were punished. 3
Because astrologers only see the future in vague terms, not in detail. Refer to Sh'mos 1:22:2:1**.
Ramban: Because they all grumbled.
Ramban: The distinction 0s based on the fact that, by the earlier incident, they quarreled with Moshe and tested Hashem (as the Pasuk writes clearly there), whereas here they quarreled with Hashem and not with Moshe. See also R. Chavel's footnotes..
How was Hashem sanctified "by them"?
Rashi and Ramban #1 (citing Ibn Ezra) 1 : Because Moshe and Aharon died as a result of the water of Merivah, and when Hashem performs judgment with those who are close to Him, people fear Him and He becomes sanctified. 2
Ramban #2: By producing water in the presence of all of Yisrael. 3
Rashbam: By producing water even though Moshe and Aharon did not speak to it.
Seforno: By performing miracles when the well defied the laws of nature by traveling upwards, as described later in the Parshah. 4
What does "Bam" refer to?
It refers to the waters of Mei Merivah, either directly or via the death of Moshe and Aharon, who died on account of them. 1