In this week’s parsha we are given the following commandment:
לֹא תֹסִפוּ עַל־הַדָּבָר אֲשֶׁר אָנֹכִי מְצַוֶּה אֶתְכֶם וְלֹא תִגְרְעוּ מִמֶּנּוּ לִשְׁמֹר אֶת־מִצְות יְהוָה אֱלֹהֵיכֶם אֲשֶׁר אָנֹכִי מְצַוֶּה אֶתְכֶם׃
You shall not add anything to what I command you or subtract from it, but keep the commandments of the LORD your God that I enjoin upon you.
The rulings laid out in the Torah are enough and exact. We are not to add to, nor subtract from, that which God commanded. The question, of course, is what exactly would count as violating these two prohibitions. Rashi explains:
לא תספו. כגון חמש פרשיות בתפלין, חמשת מינין בלולב, וחמש ציציות, וכן ולא תגרעו:
YOU SHALL NOT ADD — Like five chapters in the Tefillin, five species in the fulfillment of Lulav, and five tzitzis; likewise “you shall not subtract.”
Tefillin are supposed to contain only four parshios, and we are thus prohibited from trying to “improve” the mitzvah by adding another parsha to them. Similarly, the mitzvah of lulav requires four species, not more, as the mitzvah of tzitzis require four strings and no more. One must not add too, nor subtract from these requirements.
One cannot help but wonder, though, why these specific examples were chosen by Rashi to illustrate his point. To explain this, we must first turn to Tosafos in Rosh HaShanah (16b) that wonders why the fact that we blow 100 kolos from the shofar on Rosh HaShanah, when the Biblical requirement is to only blow nine, is not in violation of “adding to” the mitzvos. Indeed, what about eating matzah for eight days instead of the Biblically prescribed seven, or similar “additions?” Would such acts be in violation of our posuk’s prohibition?
Tosafos explains that since such acts are not changes to the essential mitzvah, they would not violate our posuk. Adding an additional parsha to tefillin, or an additional species to the lulav, is changing the essential makeup of the mitzvah itself. Simply putting on tefillin, or shaking the lulav, more than once a day is not actually adding to the mitzvah itself. It’s simply performing the mitzvah more times than is strictly speaking necessary. This sort of action is not at all prohibited by our posuk.
We can now turn to the final clause of Rashi’s comment above. Why does Rashi need to add the phrase “likewise ‘you shall not subtract.’?” Surely, we already knew that subtracting from the mitzvos is prohibited as well from the text of the posuk itself! What does Rashi add by explicitly including this prohibition again in his commentary?
R. Avigdor Bonchek makes the case (quoting from Maharsha) that the entire prohibition of subtracting from the Torah is rather strange. If this prohibition means that one cannot simply delete one of the commandments from the Torah, such a thing would seem to be blindingly obvious. Why would we need a specific prohibition against this? After all, if we could all simply choose to erase the prohibitions that we do not like, the Torah would cease to be in the first place! If, however, the prohibition here is actually not to subtract from a mitzvah itself — to place only three parshios in the tefillin, or only three species in the lulav, etc. — then things begin to make sense. Though you might think you would get partial credit, as it were, for doing “part” of the mitzvah, Rashi’s additional clause explains that this is not so. Rather, subtracting from the essential nature of a mitzvah is prohibited in the same way that adding to the essential nature of a mitzvah is. Our posuk is not concerned with adding or subtracting full commandments from God’s Torah — doing so is obviously prohibited and anyways wholly illogical — but instead comes to prohibit any attempts at altering a mitzvah itself. Surely, God’s word does not need our editing.