The parasha starts off with Moshe highlighting his desire to enter Eretz Yisrael. He describes Hashem’s response: "Hashem got very angry at me lma’anchem (for you) and did not listen to me" (Devarim 3:26). What does "for you" mean in this context?
Rashi (based on the Targum) says that it means that Bnei Yisrael caused him to be excluded from the Land. The recount of Tehillim (106:32) indicates this as well: "They caused anger at the waters of quarreling, and it was bad for Moshe because of them." The Ramban also explains that not only did their sins cause them grief, but they did for Moshe as well.
Midrash Tanchuma has a fascinating approach to the exchange. Hashem told Moshe: I made two oaths: 1) You will not enter the Land; 2) I will not destroy Bnei Yisrael. I cannot undo both. If you would like to live and Bnei Yisrael will be destroyed, this can be done. Moshe responded that he and a thousand like him should die and one of Yisrael should not be lost. This explains the linkage between Moshe and Bnei Yisrael, alluded to in the pasuk. However, no explanation is offered for the rationale of the linkage between the oaths.
The Pesikta takes yet another approach. "For you" refers to the prospect of Moshe leading Bnei Yisrael during the time of techiyat hametim (resurrection of the dead). This neither seems to be strongly supported by the simple meaning of the pasuk nor explains the connection to techiyat hametim. Yalkut Shimoni says that we learn a moral lesson from the episode. Moshe claimed that he was to die because he had spoken negatively about Bnei Yisrael. If Moshe, who had spoken mildly against Bnei Yisrael, was excluded from the Land for that reason, imagine the sin of someone who speaks very harshly against them.
The Meshech Chochma points out that several p’sukim later Moshe returned to the theme of not entering Eretz Yisrael, this time connecting it to the warning to avoid idolatry upon entering the Land. What is the point of the connection? Many cultures confer god-like status to human beings, which is diametrically opposed to authentic Judaism. The generation of Jews who left Egypt knew Moshe as one who had grown up in their midst and, with all due respect to him, did not treat him as a deity. However, says the Meshech Chochma, regarding the new generation who knew Moshe only as the godly leader who separated himself from his wife, did not eat for 40 days and nights, and otherwise was other-worldly, there was a real fear that he would be seen as idol in the most real sense of the word. Therefore, Moshe had to die before they entered the Land lest Bnei Yisrael make a mistake in this regard. How great must the precautions be to avoid cardinal misconceptions in the basic tenets of Judaism!