(א) אֵ֣ת כׇּל־הַדָּבָ֗ר אֲשֶׁ֤ר אָנֹכִי֙ מְצַוֶּ֣ה אֶתְכֶ֔ם אֹת֥וֹ תִשְׁמְר֖וּ לַעֲשׂ֑וֹת לֹא־תֹסֵ֣ף עָלָ֔יו וְלֹ֥א תִגְרַ֖ע מִמֶּֽנּוּ׃ {פ}
(א) כי גם את בניהם ואת בנותיהם ישרפו באש לאלהיהם שהוא דבר מתועב לפני השם לשפוך דם נקי ואף כי להיות אכזרי על פרי בטן לא ירחמו ועל כן אמר (דברים י״ג:א׳) את כל הדבר אשר אנכי מצוה אתכם וגו' להזהיר על מעשה הקרבנות ועבודת המקדש שלא תוסיף עליו ולא תגרע ממנו וזה ענין הפרשה הזאת באמת
(1) TAKE HEED TO THYSELF THAT THOU BE NOT ENSNARED TO FOLLOW THEM, AFTER THEY ARE DESTROYED FROM BEFORE THEE. For even their sons and their daughters do they burn in the fire to their gods,94Verse 31. it being an abominable thing before G-d to shed innocent blood,99Isaiah 59:7. and all the more to be cruel and have no pity on the fruit of the womb.100Ibid., 13:18. [Hence any form of service instituted by people capable of such cruelty is considered an abomination by G-d and no ceremony of theirs is to be adopted by us.] Therefore, he stated All this word which I command you, that shall ye observe to do,101Further, 13:1. the reference being to the performance of the offerings and the Service in the Sanctuary that thou art not to add thereto, nor diminish from it.101Further, 13:1. This is in truth the purport of this section.
In my opinion, even if someone devised an independent commandment [rather than altering an existing one] such as establishing a festival in a month which he had devised of his own accord,29I Kings 12:33. as Jeroboam did,29I Kings 12:33. he transgresses the negative commandment [Ye shall not add unto the word which I command you]. And so did the Rabbis say with reference to the reading of the Scroll of Esther [on Purim]:30Megillah 14 a. “One hundred and eighty prophets31In our text of the Talmud: “Forty-eight prophets.” See my Hebrew commentary, page 360. arose in Israel and they did not diminish from nor add even one letter to what was written in the Torah, except for reading the Scroll of Esther [which was instituted by the prophets]. What basis did they have for that? etc.”32“Rabbi Chiya bar Abbin in the name of Rabbi Yehoshua ben Korcha said: It is a matter of kal vachomer (reasoning from minor to major): If [when Israel was delivered] from slavery to freedom they sang [in praise of G-d], how much more ought they to do so when they were saved from death [that was decreed upon Israel through the plot of Haman] to life!” (Megillah 14 b). The reading of the Scroll of Esther constitutes the praise to G-d for our deliverance (ibid.). And in the Yerushalmi it is stated:33Yerushalmi Megillah I, 7. On the term “Yerushalmi” see Vol. III, p. 192, Note 44. “Eighty-five elders, among them many prophets, were troubled about the matter [of the new duty to read the Scroll of Esther]. They said, ‘It is written, These are the commandments which the Eternal commanded Moses.34Leviticus 27:34. These are the commandments that [we] were ordered by the mouth of Moses, and Moses told us that no other prophet is destined to establish anything new for you — and Mordecai and Esther want to establish something new for us!’ They did not move from there while discussing the matter, until the Holy One, blessed be He, enlightened their eyes [and they found the new commandment intimated in the Torah, Prophets, and Writings].” Thus you see that [the institution of] this commandment [of reading the Scroll of Esther on Purim] would have been forbidden to them [were it not for the fact that ultimately they found it intimated in the Torah, etc.]; otherwise it would have been included in the principle, thou shalt not add thereto.35Further, 13:1. — It should be noted that at this point Ramban cites the later verse (13:1) instead of the verse here. The reason would seem to be that the verse here relates to adding to, or diminishing from, a Divine commandment, such as placing five sections of the Torah, or only three, in the phylacteries instead of the four sections ordained. The verse of 13:1, however, refers to adding a completely new commandment to the number of Taryag (613) Commandments, or of abolishing altogether one of the Divine precepts. In speaking, therefore, of the prophetic precept of reading the Scroll of Esther on Purim, Ramban thus rightly cites the verse from further on (13:1), for were it not that the prophets and Sages of that time found it intimated in the Torah, the prohibition against instituting such a new commandment would have come under the admonition, thou shalt not add thereto. However, the prohibition against adding [to the Torah] by word of a prophet we derive only from the verse stating, These are the commandments,34Leviticus 27:34. which establishes,36Torath Kohanim, at end of Bechukothai. “From now on, no prophet is permitted to originate anything [in the Torah].” Whatever [laws] the Sages have established in the nature of “a fence [around the Torah],” such as the secondary degrees of forbidden marriages37Yebamoth 21a-b. — that activity of [establishing fences] is itself a requirement of the Torah, provided only that one realizes that these [laws] are a result of a particular fence and that they are not [expressly] from the mouth of the Holy One, blessed be He, in the Torah.38In other words, the duty devolving upon the Sages to establish “fences” [i.e., safeguards against trespassing the law of the Torah] is specifically stated in the Torah, but the precise terms of these “fences” are not written. — The duty of establishing such preventive Rabbinical laws is based on the verse, ushmartem eth mishmarti (and ye shall keep My charge — Leviticus 18:30), tradition interpreting this to mean: “Make a mishmereth (a protection, a fence as a safeguard) l’mishmarti (for My commandment)” (Yebamoth 21 b).
(10) When you have eaten your fill, give thanks to your God יהוה for the good land given to you.

