Re'eh: on the (prohibited?) evolution of Torah

Blessed are You, Adonoy our God, King of the Universe, Who sanctified us with His commandments and commanded us to be engrossed in the words of Torah.

Nonbinary Hebrew Project:
B’rucheh ateh Khavayah Shekhinu ruach ha’olam asher kidash’tanu b’mitzvotei’he v’tziv’tanu la’asok b’divrei Torah

Feminine God Language:
Brukhah at Ya Elohateinu ruach ha’olam asher keir’vat’nu la’avodatah v’tziv’tavnu la’asok b’divrei Torah

Be careful to observe only that which I enjoin upon you: neither add to it nor take away from it. If there appears among you a prophet or a dream-diviner, who gives you a sign or a portent, saying, “Let us follow and worship another god”—whom you have not experienced —even if the sign or portent named to you comes true, do not heed the words of that prophet or that dream-diviner. For your God יהוה is testing you to see whether you really love your God יהוה with all your heart and soul. It is your God יהוה alone whom you should follow, whom you should revere, whose commandments you should observe, whose orders you should heed, whom you should worship, and to whom you should hold fast.

לא תסף עליו THOU SHALT NOT ADD THERETO — as, for instance, to place five chapters in the Tephillin, to employ five species of fruit and plants in the fulfilment of the command of Lulab, to recite four instead of three blessings in the Benedictions of the priests (Sifrei Devarim 82:4; cf. Rashi on Deuteronomy 4:2).

לא תוסף עליו, for you might add something which is despicable in the eyes of the Lord. If, perchance, you would add new ways of the serving the Lord, you have no assurance that such innovation is acceptable to G’d, for instance the burning of one’s children in G’d’s honour.

ולא תגרע ממנו, even if, in your judgment, the rationale for observing the commandment in question no longer applies, is no longer relevant. An example would be Solomon’s reasoning that the restrictions placed by the Torah on the number of wives a king may have did not apply to him as none of these wives could possibly incite him to turn away from G’d. (compare Sanhedrin 21).

§ Ulla said that Reish Lakish said: If one separated ten animals for the purpose of his Festival peace-offering, and he sacrificed five of them on the first day of the Festival, he may return and sacrifice the remaining five on the second day of the Festival, or on any of the other days. There is no concern for the prohibition of: “You shall not add” (Deuteronomy 13:1), as though he were celebrating the first day twice, because the remaining offerings merely complete the first day’s offerings. Rabbi Yoḥanan said: Since he stopped after the first five offerings on the day on which he first brought the Festival peace-offerings, he may no longer sacrifice the remaining animals on the other days, as that would be considered celebrating an extra day.

It is clear and explicit in the Torah that it is [God's] commandment, remaining forever without change, addition, or diminishment, as [Deuteronomy 13:1] states: "All these matters which I command to you, you shall be careful to perform. You may not add to it or diminish from it," and [Deuteronomy 29:28] states: "What is revealed is for us and our children forever, to carry out all the words of this Torah." This teaches that we are commanded to fulfill all the Torah's directives forever.
It is also said: "It is an everlasting statute for all your generations," and [Deuteronomy 30:12] states: "It is not in the heavens." This teaches that a prophet can no longer add a new precept [to the Torah].
Therefore, if a person will arise, whether Jew or gentile, and perform a sign or wonder and say that God sent him to:
a) add a mitzvah,
b) withdraw a mitzvah
c) explain a mitzvah in a manner which differs from the tradition received from Moses, or
d) if he says that the mitzvot commanded to the Jews are not forever, but rather were given for a limited time,
he is a false prophet. He comes to deny the prophecy of Moses and should be executed by strangulation, because he dared to make statements in God's name which God never made.
God, blessed be His name, commanded Moses that this commandment is for us and our children forever, and, God is not man that He speak falsely.

A court has the authority to issue a decree and forbid something which is permitted and have its decree perpetuated for generations to come. Similarly, it has the authority - as a temporary measure - to release the Torah's prohibitions. What then is the meaning of the Scriptural prohibitions Deuteronomy 13:1: "Do not add to it and do not detract from it"?
The intent is that they do not have the authority to add to the words of the Torah or to detract from them, establishing a matter forever as part of Scriptural Law. This applies both to the Written Law and the Oral Law.
What is implied? The Torah states Exodus 23:19: "Do not cook a kid in its mother's milk." According to the Oral Tradition, we learned that the Torah forbade both the cooking and eating of milk and meat, whether the meat of a domesticated animal or the meat of a wild beast. The meat of fowl, by contrast, is permitted to be cooked in milk according to Scriptural Law. Now if a court will come and permit partaking of the meat of a wild animal cooked in milk, it is detracting from the Torah. And if it forbids the meat of fowl cooked in milk saying that this is included in "the kid" forbidden by the Scriptural Law, it is adding to the Torah.
If, however, the court says: "The meat of fowl cooked in milk is permitted according to Scriptural Law. We, however, are prohibiting it and publicizing the prohibition as a decree, lest the matter lead to a detriment and people say: 'Eating the meat of fowl cooked in milk is permitted, because it is not explicitly forbidden by the Torah. Similarly, the meat of a wild animal cooked in milk is permitted, because it is also not explicitly forbidden.' "And another may come and say: 'Even the meat of a domesticated animal cooked in milk is permitted with the exception of a goat.' And another will come and say: 'Even the meat of a goat is permitted when cooked in the milk of a cow or a sheep. For the verse mentions only "its mother," i.e., an animal from the same species.' And still another will come and say: 'Even the meat of a goat is permitted when cooked in goat's milk as long the milk is not from the kid's mother, for the verse says: "its mother."' For these reasons, we will forbid all meat cooked in milk, even meat from fowl."
Such an approach is not adding to the Torah. Instead, it is creating safeguards for the Torah. Similar concepts apply in all analogous situations.