I have held off asking this question for a while because I have only seen the premise in parsha flyers at chabad but a chance look at Wikipedia gave me the sources (below).
It is said that certain mitzvos will be nullified in the time of the Mashaich.
How then, will God be able to communicate his will that certain mitzvos are nullified?
- If God sends a prophet, if a prophet attempts to nullify a mitzva, he is considered false prophet.
- If God uses a "voice from heaven," we already have a precedent that voices from heaven don't influence halacha (lo ba shamaim hi).
- If God makes everyone "know" that the Mitzvos are nullified, they still can't go against halacha or vote on it.
The majority view of classical rabbis was that the commandments will still be applicable and in force during the Messianic Age. However, a significant minority of rabbis held that most of the commandments will be nullified by, or in, the messianic era. Examples of such rabbinic views include:
- that today we should observe the commandments (Babylonian Talmud, Tractate Avodah Zarah 3a, 4b); because we will not observe them in the world to come (Rashi)
- that in the future all sacrifices, with the exception of the Thanksgiving-sacrifice, will be discontinued (Midrash Vayikra Rabbah 9:7)
- that all sacrifices will be annulled in the future (Tanchuma Emor 19, Vayikra Rabbah 9:7)
- that God will permit what is now forbidden (Midrash Shochar Tov, Mizmor 146:5)
- that most mitzvot will no longer be in force (Babylonian Talmud, Tractate Niddah 61b and Tractate Shabbat 151b).