1) HALACHAH: MOUNTAIN WILLOWS
QUESTION: The Gemara records a number of Beraisos that discuss the laws of Aravos. The first Beraisa says that one must use Aravos that grow near a river (this implies that Aravos from anywhere else may not be used). The Gemara cites another Beraisa that says that one may use Aravos from an irrigated field or from the mountains (where there are no rivers).
How are the two Beraisos to be reconciled?
(a) RASHI (33b, DH Arvei Nachal) explains that, l'Chatchilah, a person should use Aravos from a tree that grows near a river. However, b'Di'eved, one may use Aravos from any Aravah tree. The Torah teaches only which Aravah is preferable l'Chatchilah.
The TUR (end of OC 647) writes that this is the opinion of most Rishonim. Therefore, l'Chatchilah one should use Aravos from a tree that grows near a river or stream.
(b) TOSFOS (DH v'Rabanan) points out that the second Beraisa permits Aravos from the mountains only because the verse uses the word, "Arvei," in the plural form. However, the Halachah follows the view of Rebbi Yishmael who derives from the word "Arvei" a different law -- the number of Aravos that must be used (two). Since the word "Arvei" teaches the number of Aravos that must be used, there is no source that permits Aravos from the mountains. Therefore, Aravos that do not grow near a river or stream should be invalid even b'Di'eved.
(c) The ROSH and RITVA explain that the first Beraisa does not mean that one must use only Aravos that grow near a river. Rather, it means that one should use the species of Aravos that normally grows near a river. This part of the Beraisa teaches the same thing as the second part of the Beraisa ("Davar Acher"), which states that one should use an Aravah that has long leaves that resemble a river, and not a "Tzaftzefah" that has round leaves. The Beraisa describes the species of Aravah which one must use, and not the location in which it must grow.
The Rosh adds that this is consistent with the common practice, as no one is stringent to use only Aravos that grow next to a river.
This appears to be the opinion of the RAMBAM (Hilchos Sukah 7:3) as well. The Rambam does not mention that the Aravos must grow next to a river. He says only that they must come from the type of tree that grows near a river.
HALACHAH: The MISHNAH BERURAH (OC 647:3) rules that it is not necessary to search for an Aravah that grows near a river.
2) HALACHAH: USING MORE THAN THE PRESCRIBED NUMBER OF "MINIM"
OPINIONS: The Mishnah teaches the number of each of the Arba'as ha'Minim that one must use for the Mitzvah. The Halachah follows the view of Rebbi Yishmael who says that one must hold one Lulav, one Esrog, two Aravos, and three Hadasim.
May one use more than the prescribed number of each Min (for example, ten Hadasim)?
(a) A number of Rishonim rule that one may add as many of each Min as he wants. Their ruling is based on several considerations. First, the Gemara earlier (31a) explains that according to the Rabanan, who maintain that there is no requirement to bind the Lulav with the other Minim ("Lulav Ein Tzarich Eged"), the Minim stand alone. Hence, when one adds an extra one of any Min, that extra one stands alone as well and there is no concern for Bal Tosif (the prohibition against adding to the Mitzvos).
Although the Beraisa there states that one may not add to the Arba'as ha'Minim, and the Beraisa seems to follow the Rabanan (who maintain that each Min stands alone, and thus Bal Tosif does not apply), that Beraisa refers to non-Minim. The Rabanan prohibited one from adding a species which is not one of the four Minim in order to prevent one from thinking that the added Min (such as a eucalyptus branch) is one of the Arba'as ha'Minim required by the Torah. The Rabanan did not prohibit one from adding an extra one of the Arba'as ha'Minim themselves. (RITVA, 31b)
Since the Halachah follows the view that the Lulav does not need to be bound with the other Minim, one should be permitted to add more of the Arba'as ha'Minim. (According to the opinion that a Lulav must be bound with the other Minim, adding another type of Min is forbidden mid'Oraisa, and adding another one of the Arba'as ha'Minim is forbidden mid'Rabanan. The only reason why one may use a Lulav leaf to tie together the Lulav, Aravos, and Hadasim is because it does not stand upright like a Lulav, and thus there is no concern for Bal Tosif.)
Second, even if the Rabanan prohibited one from adding a different type of Min as a rabbinical application of Bal Tosif (and not because of the concern that one might mistakenly think that this Min is one of the four which the Torah requires), they still permitted one to add one of the Arba'as ha'Minim. According to some Rishonim, the prohibition of Bal Tosif does not apply when one performs a single Mitzvah twice, but only when one adds to the Mitzvah a different item (which is not an item of the Mitzvah at all). (TOSFOS)
A third reason for why the Rishonim permit one to use more than the required amount of the Arba'as ha'Minim is because the Torah does not specify the number of Esrogim, Lulavim, Aravos, and Hadasim that one must use. Rather, the Torah merely gives the minimum number that one must use (at least one Esrog, one Lulav, two Aravos, and three Hadasim). Therefore, there is no problem of Bal Tosif if one adds more than the prescribed number. (RITVA, 31b)
(b) The RAMBAM (Hilchos Lulav 8:7) rules that one may add only to the number of Hadasim, because Hadasim add to the beauty of the Lulav. When one adds to a Mitzvah in order to beautify it, Bal Tosif does not apply. This is also the opinion of the RASHBA (Teshuvos 1:75).
According to a variant text of the Rambam's words (see the RAN here), the Rambam says that an Aravah may also be added because it, too, adds to the beauty of the Mitzvah.
(c) The SHIBOLEI HA'LEKET (#358) rules that one may a Hadas and Aravah, but not a Lulav and Esrog. This is derived from the verse in which the Torah mentions the Hadas and Aravah in the plural form, and the Lulav and Esrog in the singular form (see 32a and 35a). The verse teaches that one may not use more than one Lulav or more than one Lulav.
(d) According to all of the opinions mentioned above, one may add more Hadasim to the Lulav. However, the ROSH cites the GE'ONIM who permit one to add Hadasim only if they are Meshulashim. A Hadas which is not Meshulash (such as a "Hadas Shoteh") is a different species and therefore may not be added to the Hadasim.
The RITVA (31a) gives another reason for why one should not add a "Hadas Shoteh." As the Ritva explains (see (a) above), the reason why one may not add a non-Min to the Arba'as ha'Minim is because one might think that the non-Min is one of the Minim that the Torah requires for the Mitzvah. Therefore, one may not add a "Hadas Shoteh" (which is invalid for the Mitzvah), lest one think that it may be used for the Mitzvah. (See also Insights to Rosh Hashanah 28:2:a.)
HALACHAH: The SHULCHAN ARUCH (OC 651:15) first cites the opinion of the Shibolei ha'Leket and the opinion of the Rambam (according to the alternate text), who permit one to add to the number of Hadasim and Aravos, but not to add a Lulav or Esrog. The Shulchan Aruch then cites the opinion of the Ge'onim who do not permit one to add a "Hadas Shoteh."
The Shulchan Aruch concludes that those who are scrupulous in their observance of the Mitzvos do not add to any Minim, even to the Hadasim and Aravos. The MISHNAH BERURAH (651:60) adds that one who wants to add to the Minim should have intent to add for the sake of beautifying the Mitzvah.