Thus, the Lubavitcher Rebbe believed that Rashi anticipated a potential question as a result of Moshe's ambiguous status. When Moshe brought [the inaugural ram] up in smoke on the altar, one could ask why he burned the right thigh as the Torah reserved the right thigh of any peace offering as a gift for Kohanim (Vayikra 7:32). But here, Moshe did not offer it to Aharon or his sons. Until now, all of Moshe's actions can amount to following G-d's command, but how could a Levi choose to burn a gift for the Kohanim? That does not sound like a command from Hashem. Therefore, we might have concluded that Moshe was elevated to the status of a Kohein, so Rashi chose this moment to explain that Moshe wore a white robe during the seven days of inaugural service, not the Bigdei Kehunah. True, he was not a Kohein like Aharon as the priestly garments were still off-limits to him. However, there was something different at this time, a special elevated status just for the Shivat Yemei HaMiluim. Moshe's white robe was not considered Bigdei Kehunah, nor was it meant to be. Perhaps he wore it to reflect a change in his own personal status, even if only for a brief moment in time.
With that background, one might suggest a thematic connection between the three questions from the story in the Gemaras. Upon further investigation, the first two questions each introduce one aspect of the ambiguity surrounding Moshe's role during the inaugural service. First, we learn that the halacha does indeed recognize a short fast as binding, and furthermore, if one completed the fast, he would recite Aneinu in his Amidah (Avodah Zarah 34a). While no one would claim that a half-day is longer than a whole day, we find that the status of a few hours can be elevated to have the same halachic impact as a whole day. Similarly, no one would claim that a Levi outranks a Kohein, but the Torah describes one special week when a Levi seemed to have the same halachic impact as a Kohein. Next, we learn that an idolator's jugs are forbidden if they carry the taste of his wine, but over time the taste goes away and the jug becomes permissible. The combination of the taste of an idolator's wine and kosher wine was problematic; Lehavdil, it was no better than a Levi wearing priestly garments. Once the forbidden mixture is gone, the jug can serve as a dignified vessel for kosher wine. Now, a familiar progression emerges. It is possible to elevate one's status for a short span of time, so Moshe could be a Kohein for a week. We also know that individual elements of a forbidden combination are permissible, but we find no description of Moshe Rabbeinu's dignified vessel. What did he wear during that special week of service? Thus, the Gemara records that Moshe's white robe served as the vessel for an elevated spiritual status in time.
On Shabbat HaGadol we recall how our forefathers prepared to fulfill the Mitzvah of Korban Pesach in Mitzrayim. In the introduction to his commentary on the Haggadah, the Netziv identifies this as the reason for the Ashkenazic Minhag to wear a Kittel on Pesach night. He believes our job at the Seder is to act as our forefathers did at the time when they would bring the Korban Pesach. He describes how the Jews in Yerushalayim would wear a white robe of cotton to demonstrate the sanctity of these precious moments. Just as the right thigh belongs to the Kohein by right, the Korban Pesach must be treated as a gift to us from Hashem's table, MiShulchan Gavoha, From a higher table and as such we must approach this Mitzvah with awe; as if one were to dine with the king (Imrei Shefer, Peticha). If we are to experience an elevated spiritual status on this night, it is fitting that we wear a Kittel.
In essence, there is a custom at the Seder in order that we are to emulate Moshe. He wore a Kittel when HaKadosh Baruch Hu gave him the chance to be more, and we do the same. Even if we struggle with insecurities and imperfections in our regular service, we believe that these few hours on these few nights can have more impact than other hours on other nights. We don our white robe as a dignified vessel to reflect our elevated spiritual status, and we must allow the taste of this combination to linger after the Seder. We pray that in the merit of our Avodah during this special time, we will soon see the coming of Mashiach and join together to partake of the Korban Pesach in Yerushalayim.
