"He [G-d] who is everlasting, constant, and in no way subject to change; immutable in His Essence, and as He consists of nought but His Essence, He is mutable in no way whatever; not mutable in His relation to other things: for there is no relation whatever existing between Him and any other being, as will be explained below, and therefore no change as regard; such relations can take place in Him. Hence He is immutable in every respect, as He expressly declares, "I, the Lord, do not change" (Mal. 3:6).
– Part 1, Chapter 11, verse 2.
And G-d is, “the stable one who undergoes no manner of change…nor a change in His relation to what is other than Himself” - Guide 1:11 (emphasis added). Yet some acts are not even commanded in the Torah but the rabbis made them as to show love of G-d. Moshe said you cannot add to the law. But these rabbis weren’t adding. These expressions are the divine Will. The rabbis have derived these acts through celebration and delving into the Torah with deep study (immersed in Torah study). But these exquisite commands are not alluded nor nuance in text. They are sensed. Take for instance the rabbinical enactments, safeguards, customs and embellishments (hiddur mitzvah). The community also sends gifts and food on Purim, not a biblical law found the Torah. We eat fruits on Tu B’Shvat, and even celebrate (dance) with the Torah when finished reading.
Nevertheless G-d expects us add fences to the biblical laws. For instance, an eye for an eye is to mean compensation as in payment.
Another example are the sacrifices. G-d neither needs nor wants sacrifices, and only allowed it because people in ancient times felt differently. It is a concession to human needs. The Rambam also states that this is not only his view but is the view of the prophets.
We can add that the ancient rabbis around 70 CE when the temple was destroyed also felt that sacrifices were unnecessary. Therefore when the temple was destroyed, they did not seek a way to continue sacrifices. It would have been easy for them to do so if they felt it was necessary.
Of course, as is to be expected, many rabbis disagreed. We still have many references in the siddur praying for the restoration of sacrifices. But the siddur is a compendium of many often conflicting ideas, which prompt us to think and to remember the past.
In the Babylonian Talmud, Nidah 61b, Rabbi Joseph says: “The mitzvot [commandments] will be abolished in the time to come (WtC).” Apparently, rabbis’ Abraham and Joshua Flak are in agreement. In his Sefer Ha-ikkarim, 14th-century rabbi Joseph Albo says that a future prophet may abolish or nullify all of the biblical commands except for the Decalogue, given that he has authority from Hashem. That is to say, he may do away with the Mosaic law if G-d’s voice is heard again under the canopy of six-hundred thousand people as was in the event at Sinai.
Is this person whom Albo is speaking of lives in the future Messianic earth? Maimonides said that nothing miraculous will happen except that all non-Jews will become Jews. So it appears that some say all the laws will be abolished because there will be no need for repairs. Yet others say that if a future prophet appears and claims to nullify the laws, Hashem must grant him authority first. Though Albo thinks this unlikely, he leaves room for its possibility.
Thus, if a prophet were to announce his prophethood to be greater then Moshe or in another country, or not at all, and whether or not he is the Moshiach, s/he must first find approval from Hashem in order to abolish or nullify the Mosaic laws (Mitzvos).
This in no way entails that Jesus (generally acclaimed to be the Messiah by Christians) or Muhammad (customarily declared to be the final prophet by Muslims) meet the requirements expressed by the views of R. Albo or Maimonides as neither of the two candidates advocate to be a good predecessor to Moshe Rabbeinu in front of mass witnesses (six-hundred thousand people) to proclaim that this is the new Will of G-d. As noted above, G-d does not change His Will but allows certain laws (sacrifices) in place of human needs, which may be removed when humanity is ready to progress.