Please have in mind that this limud should be a zechus for a refuah sheleimah for Shulamis bas Sarah Sascha.
At the end of the parsha (32:48) Hashem told Moshe to go "b'etzem ha'yom ha'zeh," this very day, up to Har Nevo, to look out over the Land, and then and to die.
Rashi points out that there are three places where the Torah uses this expression of "b'etzem ha'yom ha'zeh." The common denominator between them is that in all three places there was a hava amina by human beings to try to stop G-d, and G-d responded by carrying out his plans in the middle of the day to demonstrate that no force can stop him. When G-d was about to bring the flood, the dor ha'mabul threatened to destroy the ark; G-d in turn ordered Noach to enter in the middle of the day to prove that they could not stop him. The Egyptians thought they would prevent Klal Yisrael from leaving; G-d took them out right in the middle of the day to prove the Egyptians wrong. Finally, here, Klal Yisrael thought that they would cling to Moshe and not let him die; G-d arranged his death in the middle of the day.
We understand the hava amina of taking axes and breaking the ark; we understand the hava amina of taking up arms to stop Klal Yisrael from leaving Egypt. But how could Klal Yisrael have even had a hava amina of stopping Moshe's death? What power do human beings have to stop someone from dying?
R' Chaim Shmuelevitz answers that the power we have is the koach ha'tefilah.
The gemara (Kesubos 104) tells us that when Rebbi was about to die, the tefilos of his generation kept him on earth until, seeing his suffering, his maid caused an interruption to the prayers so that Rebbi could depart this world in peace.
We just said over the Yamim Noraim that teshuvah, tefilah, and tzedaka can avert an evil gezeirah.
Now that we know the power our tefilah has, I have a simple kashe: so why didn't it work? Why did the tefilos of Klal Yisrael keep Rebbi in this world, clinging to life, but G-d forced Moshe "b'etzem ha'yom ha'zeh" to pass away irrespective of what Klal Yisrael wanted and davened for?
I think the answer to the question is rooted in the nature of Moshe's sin at mei meriva. Netziv on our pasuk briefly reminds us of his interpretation of that episode, which he elaborates on more fully in Chukas. Hashem wanted mei meriva to be a "teachable moment," as they call these things in the world of education. It would be another step in the transition from life in the desert surrounded by miracles to the life of teva in Eretz Yisrael. What do you do when you life in the world of teva and you face a drought? Hashem wanted Moshe to show the people that the answer to their needs would come through tefilah and Torah study. That's how we who live in the mundane world approach G-d with our needs. But that's not what Moshe did. Instead, he hit the rock, and through a miracle -- much like the other miracles that happened in the desert -- the rock produced water. In response, Hashem told Moshe that since he was stuck in the miracle mode of desert life and could not transition to the teva life of Eretz Yisrael, he would not be the one to lead the people there.
Moshe now in our parsha must pay the ultimate price for his sin and die before entering the land. Al asher m'altem bi... b'mei merivas Kadesh..." I think is not merely a reminder of what Moshe did wrong, but is an explanation of why tefilah here did not work. Because he did not capitalize on the koach ha'tefilah to meet the people's needs at Mei Merivah, midah k'neged midah, the koach ha'tefilah could not work on Moshe's behalf here to spare him from his fate.
At this special time of year may all our tefilos for all our needs be speedily answered.