Or HaChaim on Numbers 27:13/אור החיים על במדבר כ״ז:י״ג

1 וראיתה אתה "and when you have seen it, etc." G'd did not limit Himself to the previous words וראה את הארץ, "and view the land, etc," in verse 12. The Torah wanted to indicate that Moses was enabled to see the land by means of a miracle, i.e. his power of vision was expanded. What Moses beheld could not be seen by ordinary man who is equipped to see only with the help of sunlight; rather it was required that G'd put at Moses' disposal the light which G'd had hidden after Adam had sinned, the light created on the first day of creation (compare Sifri volume 1 item 136). This is also the light G'd put at Moses' disposal in Deut. 34,1. where He showed him the whole of the land of Israel.

2גם אתה כאשר נאסף אהרון, "also you, just as Aaron was gathered in, etc." This is best explained by reference to Yalkut Shimoni at the beginning of Parshat Massay. We are told there that when Aaron was about to die he told Moses that had he known death was something so pleasant he would have wanted to die even sooner. The Torah wrote גם אתה "also you" immediately next to the word ונאספת, "you will die," in order for Moses to understand that his own death would be just as pleasant as that of his brother Aaron had been. When Moses would realise the nature of his death he too would wish that he had died even sooner. An additional meaning of these words is that G'd wanted Moses to do what all righteous people are supposed to do before they die, namely to acknowledge that G'd's justice as applied to them was fair. The person who is about to die should welcome G'd's decision that he die at that time. By saying: "also you will be gathered up to your people," G'd hinted that Moses should acknowledge the justice of G'd's decree in letting him die at this time and at this place. The classic example for this type of attitude is King David in Psalms 31,6 where he said: "I place my spirit in Your hand."

3The Torah continues "just as Aaron was gathered in," to reflect a further comment by the Yalkut there who quotes Moses as having asked his brother Aaron at the time if he accepted the need to die. When Aaron had replied in the affirmative, Moses said to him: "let us ascend the mountain. Immediately following this suggestion Moses and Aaron (and Eleazar) ascended the mountain. Thus far the Yalkut. This is what the Torah alludes to with the words: "as your brother Aaron was gathered in." The reason for all this was that G'd did not want to let a righteous person die without first gaining his consent. This will also afford the person about to die to fulfil the commandment in Deut. 6.5 to love G'd "with all your soul."