Question:

Are there any sources in the Torah that discuss how the seventh day of Pesach will be celebrated in the times of Moshiach?

Answer:

Rabbi Schneur Zalmen of Liadi, founder of Chabad Chassidism, originated the concept that in the times of Geulah, there will be no eating or drinking on the seventh day of Pesach! The Divine revelations on that day will be so outstanding and will elevate us to such heights of joy and spirituality that the thought of food or drink will seem strange.

These matters are based on the precision of certain expressions in the verses of the Torah. Unlike the holiday of Simchas Torah, on which the verse says, "Atzeres it will be for you," regarding the seventh day of Pesach it says, "Atzeres to G-d your L-rd." This is a holiday that is not designated for "you," but is entirely sanctified to "G-d, your L-rd." The Rebbe explains that "The verse is referring to the future, when the seventh day of Pesach will be... of an aspect... in which there will be no eating or drinking." Therefore, the day will not be "for you," for your physical desires.

For this reason, there is a verse that says, "Six days you shall eat Matzos"-- and not seven days--since in the future we will eat matza for only six days.

There is an additional hint in the expression used by the Torah to forbid doing work on the seventh day of Pesach: "You shall not do any work." From the phrasing of the verse it is apparent that even work associated with preparing food is included in the prohibition, even though such work is generally permitted on holidays and forbidden only on Shabbat. This verse is alluding to the period of Redemption, in which we will not eat at all on this day, and as a matter of course there will be no reason to permit work to prepare food.

It must be emphasized that this behavior is not a contradiction to the Mitzvah of eating and drinking on every Yom Tov. There is a clear halacha that eating and drinking on Yom Tov is a Mitzvah because it causes one to rejoice and feel pleasure. When a person feels pleasure in other ways, not through food and drink, he is not obligated to consume food. Therefore, on the seventh day of Pesach we will fulfill the Mitzvah to rejoice on Yom Tov even without eating--since we will derive pleasure from the spiritual heights of the holiday itself.

Source: Likutei Torah, Parshas Tzav, 15:4. Toras Menachem 5748, vol. 2, p. 123 and "Hosapha."