Musar על עבודה זרה 67:5

Keeping this in mind we can answer the question how Moses could have performed service in the Sanctuary during the seven days preceding the eighth day of Nissan mentioned in Leviticus 9,1. Our sages answered this question saying that Moses went in wearing a white shirt (Taanit 11). At first glance the question does not seem to fit the answer. If the questioner wanted to know whence Moses had taken the sacred vestments to enable him to perform the service in the Sanctuary -because he presumed that such service could not be performed without the sacred vestments- then the answer simply skirts the issue. If, on the other hand, the questioner did not consider the wearing of the sacred vestments as an absolute prerequisite before such service in the Tabernacle could be performed, what was the point of the question?

The Torah is telling us that if only Adam had not sinned, his body would have been as holy as the כתנות אור, the garments of light that man was meant to wear in Gan Eden. Under the circumstances, these garments have become כתנות עור, garments of skin and flesh, something physical. As long as Adam did not need those garments, he was placed in גן עדן, to help preserve it since he was not a stranger, i.e. זר, in that environment. Once he had become forced to garb himself in garments made of materials that come out of the earth he had become a stranger in that environment, and this situation did not change until Aaron became anointed by holy anointing oil as High Priest. Compare what I have written earlier in Parshat Tetzaveh, concerning Moses performing priestly functions dressed only in a white tunic instead of in the High Priest's garments. This meant that he had never been a זר, stranger, at all; the whole house filled with light at the time he was born (Exodus 2,2, as quoted in Sotah 12). Moses' unblemished condition continued until, in the end, he himself radiated light, as we know from Exodus 34,29. This is as if he had been garbed in the כתנות אור, that we described as the state of man in his innocence in גן עדן. This is what was meant by the white tunic in which he performed the sacrificial service. It meant he did not need to do anything to rehabilitate himself in order to achieve the state of holiness necessary for a High Priest to perform sacrificial service, זרות, alienation, was a condition that did not come into existence till after the כתנות אור, garments woven out of light, had been withdrawn, to be kept in hiding until the future, the time of the Messiah, just as the original light G–d had created at the beginning of the creative process had also been "hidden" due to man's sin (Compare Tanchuma Noach 3). Moses did not have to wait for that light to re-appear.

The second introductory remark concerns what I wrote in that portion, i.e. that Moses performed the priestly functions during the first seven days of the Tabernacle wearing a white tunic. Moses had been "light" ever since the day he was born and his parents' home was filled with light at his birth. He had never been a זר, "outsider," unlike his brother Aaron. He was therefore on a much higher spiritual plane than Aaron. The Midrash therefore was quite justified in pointing out that the Torah's words: "G–d called to Moses," are to alert us to the fact that only Moses qualified for this call, not even Abraham or Aaron had ever qualified to such a call.