Or HaChaim on Deuteronomy 32:50/אור החיים על דברים ל״ב:נ׳

1 ומת בהר, "and die on the mountain." G'd wanted Moses to be willing to die. G'd does not remove the souls of the righteous from their bodies unless they agree. G'd added והאסף אל עמיך, "and be gathered in to your people," this is an allusion to what the Talmud says in Ketuvot 104 that the righteous in the hereafter come out to welcome the righteous who is about to join them. G'd told Moses he was going to be met by a reception committee.

2We may also understand this as one of the three reasons G'd supplied for the death of a man of Moses' calibre. The meter of the whole verse is something like this: ומת, "and die;" the reason this was to occur on the mountain may be explained on the basis of Sotah 14. The Talmud wanted to know why Moses was buried on the mountain of Nebo and concludes that it was because of the sin of Baal Pe-or. As long as Moses would be able to look down on that idol from his grave he could hold its power in check. This is why the Torah makes a point in 34,6 to tell us that Moses' grave is opposite the temple of Pe-or. A second reason why G'd told Moses "which you are ascending," was to enable him to amass certain spiritual wealth which it would have been impossible for him to attain by the performance of good deeds on this earth as long as his soul was fused to his body. The word אשר is a reference to the celestial regions. The third reason is introduced by the words והאסף אל עמיך, "and be gathered in to your people." We can understand this in light of Bamidbar Rabbah 19 interpreting Deut 33,21 ויתא ראשי עם. "He came at the head of the people." According to this Midrash the generation of the desert would merit to partake in the resurrection only due to Moses being buried on the East Bank of the Jordan, just as they were buried there. The people considered Moses one of their very own as per Exodus 32,7 "Go on down for your people have become corrupt." The operative word here is עמיך i.e. that in order to save his people at the time of the resurrection Moses had to die here and now. While it is true that the Torah employed a similar expression at the time Aaron died, this does not prevent us from using this verse exegetically.