In the days of Rebbi Avahu (who lived about 250 years after the Churban), the Sanhedrin had long since ceased convening. It is not necessary to have a Sanhedrin to make a Takanah. Any leader of the Jewish people, with his Beis Din, can make a Takanah.

Moreover, some explain that he did not actually institute a new practice, but rather he called on all Jewish communities to blow the Shofar in the same manner (see Ya'avetz here).

Below are our Insights to Sukah 16, as you requested. I hope it is helpful

All the best,

Yisroel Shaw

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Sukah 16

1) A DISMANTLED BED QUESTION: The Gemara quotes the Mishnah in Kelim (18:9), in which we find that the Chachamim say that a slat and two legs of a bed are Mekabel Tum'ah, according to the interpretation of Rebbi Chanan in the name of Rebbi. In the Mishnah there, Rebbi Eliezer states that a bed becomes Tamei only when it is a "Chavilah," completely assembled into one unit. Likewise, in order to be Metaher it from its Tum'ah, the entire bed must be immersed in a Mikvah as one unit. RASHI explains that it only can become Tamei when it is whole, but if the parts are dismantled, they cannot become Tamei,. Even if there is a slat with two legs attached to it, which is a significant part of the bed which can be used by leaning it against a wall, nevertheless, such a configuration is not considered a complete Kli with a normal use and it cannot be Mekabel Tum'ah. When Rebbi Eliezer says that a bed can only become Tahor as a "Chavilah," he means that if a bed that became Tamei is dismantled and then immersed, it will not become Tahor.

How can it be that when the bed is immersed in separate pieces, it does not become Tahor? According to Rebbi Eliezer, the parts of a dismantled bed are not considered to be a Kli, but rather a broken Kli. We know that whenever a Kli which is Tamei is broken, it loses its Tum'ah (because it is no longer a Kli) -- which is why a bed cannot become Tamei unless fully assembled, according to Rebbi Eliezer. How, then, can Rebbi Eliezer say that the separate pieces of a dismantled bed must be reassembled and require Tevilah to become Tahor -- they are already Tahor!

ANSWERS: (a) TOSFOS, the ROSH, and the RASH (in Kelim) explain that indeed, a bed that is Tamei becomes Tahor when it is dismantled according to Rebbi Eliezer. Nevertheless, when the bed is reassembled, it will revert back to its state of Tum'ah and will need Tevilah. Tevilah does not work while it is dismantled because the Tum'ah does not return until it is reassembled.

There are two problems with this answer. First, the RASH himself asks from the beginning of the Mishnah in Kelim which says explicitly that if half of a bed was stolen, even if one gets back the stolen part and puts the bed back together, it does not revert back to its old Tum'ah that it had before it was taken apart and stolen!

Second, the Mishnah (Kelim 11:1) tells us that the only type of Kli which regains its old Tum'ah when it is repaired is a metal Kli. Other types of Kelim become Tahor when they are taken apart and remain Tahor when reassembled. The wooden bed, therefore, should also remain Tahor when reassembled! (VILNA GA'ON, Kelim 18:7)

To answer the first question, the RASH says that when half a bed is stolen , one despairs of ever putting it back together again. Therefore, it is considered to be irrevocably destroyed, and even if one does put it back together it will not revert back to its old Tum'ah. In the case of our Gemara, all the pieces of the bed are available and one plans to reassemble the bed, and thus it reverts back to its old Tum'ah when reassembled.

This might also answer the second question. Although normally, broken Kelim (that are not of metal) do not become Tamei when reassembled, this type of Kli is different. Since it is common to dismantle and reassemble beds, it is not considered a broken Kli when it is dismantled, and thus it returns to its Tum'ah when it is reassembled. However, if it is not considered broken, then why can it not be Mekabel Tum'ah when dismantled? Rebbi Eliezer is teaching that in order to be Mekabel Tum'ah, in addition to not being broken, it must also be usable. Even though the dismantled bed is not considered broken, since it is not usable it is not Mekabel Tum'ah.

(b) The VILNA GA'ON (Kelim 18:7,9) explains that when Rebbi Eliezer states that the bed is only Metamei when it is whole, he does not mean that when it is dismantled it becomes Tahor. Rather, if it was already Tamei before it was dismantled, it remains Tamei when dismantled, because it is not really considered to be a broken Kli. However, if the bed was Tahor when it was dismantled, and now a part of the bed touches something that is Tamei, it cannot become Tamei. The parts of a dismantled bed cannot acquire new Tum'ah.

Rebbi Eliezer's statement that the bed only becomes Tahor in its whole state means that it can only become Tahor when it is reassembled, but until then it remains Tamei. (It cannot be immersed in its disassembled state, because it is Tamei only due to what it used to be (a useable bed); in such a state it can only become Tahor in the same state in which it was when it became Tamei.)

(c) TOSFOS and the RASH cite sources from the Tosefta for an entirely different way of understanding Rebbi Eliezer. Rebbi Eliezer does not mean that a bed becomes Tamei only when it is assembled. Rather, he means that it becomes Tamei even when it is assembled. "Chavilah" does not mean that the bed is completely assembled; rather, it means that as little as one slat and two legs ("Aruchah u'Shnei Kera'ayim") are assembled. This means that any part of a bed that is dismantled remains Tamei, and even can become Tamei. However, if a few of the pieces of the bed are attached to each other, by touching the leg of the assemblage, the entire bundle of pieces becomes Tamei (the Tum'ah spreads to the slat and to the other leg). The Chachamim who argue say that only the parts that were touched, and they do not transfer the Tum'ah to the other pieces attached to them. Since it is not a whole bed, it is not considered a single cohesive unit to spread the Tum'ah throughout the other parts. When the bed is completely assembled, the entire bed becomes Tamei if any part of it is touched by a person who is Tameil.

When Rebbi Eliezer says that a bed becomes Tahor only when it is a "Chavilah," he means that since he considers an "Aruchah u'Shnei Kera'ayim" to be a coherent unit, one may be Tovel it all at once, and we do not say that the point at which they are connected is a Chatzitzah. The Chachamim argue and say that the parts of the Tamei bed must each be immersed separately, because the points at which they are connected are considered Chatzitzos. Only when all the parts are assembled into a complete bed is the entire bed viewed as a single unit and may be immersed all together; when the parts are not completely assembled into one complete bed, each piece is viewed as a separate part and must be immersed separately.