Chapter 23 Pasuk 34
“Speak to the Bnei Yisrael saying on the 15th day of this 7th month it will be Chag Hasukot seven days for Hashem”.
Interestingly, both our Pasuk here and Pasuk 27 which discusses Yom Kippur mention this 7th month, whereas it later in Pasuk 39 which mentions the Mitzva of Lulav the it does not mention the word this month; it only says on the 15th day of the 7th month. The Baal Haoneg Yom tov asks what is the essential difference between the Pasukim where it uses the words this month for Yom Kippur and Sukkos, but not for Lulav?
The Oneg Yom Tov cites the Gemara in Ketuvot 10b where the Gemara explains the reason that a widow is called an Almana is because an Almana is given the sum of a Mana for her Ketuva if her husband divorces her. The Gemara asks how that is possible since the Mana was an amount instituted by the Rabbis which happened many years after the Torah was given. The Gemara answers that the Torah gave the name based on the future Takana that the Rabbis would institute.
The Gemara in Rosh Hashana 29b mentions that when Rosh Hashana falls on Shabbat they would blow the Shofar only in the Mikdash but not in the Medina (define!). The Gemara explains that the Rabbis made such a decree to prevent someone from carrying the Shofar 4 amot in the public domain and thereby transgress the Shabbat. The Gemara further explains the 2 different expressions the Torah uses. In Parashat Emor (23:24) the Pasuk uses the expression Zichron Teruah and in Bamidbar (29:1) it says the phrase Yom Teruah. The expression Yom Teruah is used when Rosh Hashana falls on a weekday when we blow the Shofar and the verse Zichron Teruah is used when Rosh Hashana falls on Shabbat when we do not blow the Shofar.
The Baal Haoneg Yom Tov explains that in our Parasha the Pasuk says on the first day of the 7th month it will be a day of Zichron Teruah. This refers to when Rosh Hashana falls on Shabbat and we do not blow the Shofar because of the decree someone might come to carry. If Rosh Hashana falls on Shabbat, then Sukkot will also fall on Shabbat but Yom Kippur will fall on a Monday.
So when Yom Kippur falls on a weekday then all the Dinim are as normal and the Pasuk uses the expression this month. Also regarding Sukkot the Pasuk uses the word this month as the Mitzvah of sitting on the Sukkah remains the same even when Sukkot falls on Shabbat. However when the Torah mentions the Mitzvah of Lulav it does not mention the word this 7th month, meaning during the year that the Lulav falls on Shabbat then one is not allowed to perform the Mitzvah of Lulav because of the decree that someone might come to carry. The Mitzvah of Lulav is performed on other years when it does not fall on Shabbat and that is the reason it does not mention the word “this” month, as we refrain from performing the Mitzvah when Yom tov falls on Shabbat.
The Pasuk that speaks about Rosh Hashana when it says Zichron Teruah also does not mention the phrase this 7th month. This must also be for the same reason, as one does not blow the Shofar when Rosh Hashana falls on Shabbat.
As Chazal have told us there is nothing that is not hinted in the Torah.