OPINIONS: The Gemara lists several conditions that must be fulfilled in order to build a valid Tzuras ha'Pesach to permit one to carry in a Mavoy:

1. Rav Chisda rules that the board or cord that serves as the top of the Tzuras ha'Pesach must be resting on the top of the two side-posts. If it is resting on (or wrapped around) the sides of the posts, it is not a valid Tzuras ha'Pesach.

2. Rav Chisda also rules that the Tzuras ha'Pesach must be strong enough to support a door (even though it is not necessary to actually affix a door), but it suffices if the Tzuras ha'Pesach is strong enough to support a door made out of a light material, such as straw.

3. Reish Lakish in the name of Rebbi Yanai rules that a Tzuras ha'Pesach must have a recognizable place in which to insert a door-pivot (this refers to a small hole in the ground near one side-post of the Tzuras ha'Pesach).

4. Rav Nachman adds that there is a leniency in the laws of Tzuras ha'Pesach. The two side-posts do not need to reach the board on top (although they must be directly below it), and they even may be several Amos away from it. (They are considered to reach the top board due to the principle of Gud Asik.) Rav Sheshes argues and requires that the board actually rest on the side-posts.

The Gemara relates that the students of Rav Ashi told Rav Acha, the son of Rav Avya, that Rav Ashi did not teach any requirements for the Tzuras ha'Pesach. What does this mean? What conditions did Rav Ashi not require for a Tzuras ha'Pesach?

(a) The RA'AVAD (cited by the Ritva) explains that Rav Acha asked the students of Rav Ashi whether Rav Ashi had taught any other laws concerning a Tzuras ha'Pesach. The students answered that Rav Ashi had not taught any other laws. He did not argue with the conditions required by Rebbi Yanai or Rav Chisda, though, and thus all of those conditions are necessary. This is the ruling of the ROSH and the TUR.

Similarly, RAV YAKOV EMDEN explains that Rav Acha's father, Rav Avya, was the same Amora who explained what Reish Lakish meant by "Heker Tzir." Rav Acha wanted to know whether or not Rav Ashi disagreed with Rav Avya's explanation of "Heker Tzir." The students of Rav Ashi answered that he did not disagree, and the Halachah therefore follows Reish Lakish and Rav Avya's explanation of "Heker Tzir."

(b) The RITVA and RASHBA cite an opinion that explains that the statement of the students of Rav Ashi refers to the preceding statement in the Gemara, in which Reish Lakish states that a Tzuras ha'Pesach must have a hole for a door-pivot. The students of Rav Ashi said that Rav Ashi did not require such a hole. They were not referring to any of the other requirements.

The RIF, RAMBAM, and RIVASH rule that a Tzuras ha'Pesach does not need a hole for a door-pivot. (The ROSH suggests that these Rishonim rely on the opinion of Rebbi Yochanan which is mentioned in the Yerushalmi. Rebbi Yochanan argues with Reish Lakish and does not require a hole for a door-pivot.)

(c) The TOSFOS RABEINU PERETZ (cited by the Ritva) explains that this statement refers to the previous two statements, that of Reish Lakish (that a Tzuras ha'Pesach must have a hole for a door-pivot) and the second statement of Rav Chisda (that the side-posts must be strong enough to support a door). The students of Rav Ashi said that Rav Ashi required neither of those two conditions. This is how the RASHBA rules (Avodas ha'Kodesh 2:2:1), although he cites dissenting opinions and says that it is best to be stringent like those opinions.

(d) The RASHBA suggests further that perhaps Rav Ashi did not have any requirements for a Tzuras ha'Pesach (that is, he disagreed with all of the three previously mentioned conditions and maintained that even a "Tzuras ha'Pesach Min ha'Tzad" is valid).

QUESTION: Rav Nachman maintains that the side-posts of the Tzuras ha'Pesach do not need to reach the top of the Tzuras ha'Pesach. Even if the board or cord on top is supported by some other means, and even if it is several Amos away from the top of the side-posts, it is a valid Tzuras ha'Pesach as long as it is directly over the side-posts. The principle of Gud Asik ("the wall goes up") allows the side-posts to be considered as extended all the way up to the board or cord on top, and thereby a complete Tzuras ha'Pesach is formed. (REBBI AKIVA EIGER in the name of TESHUVOS HA'RE'EM (Rabeinu Eliyahu Mizrachi); see also MISHNAH BERURAH OC 362:62.)

If the side-posts do not have to touch the top of the Tzuras ha'Pesach because of Gud Asik, then why -- according to Rav Ashi earlier (9a) -- does the Korah that lies across the Mavoy have to actually touch the top of the walls of the Mavoy (or rest at least within three Tefachim of the top of the walls)? The Korah should be able to rest far above the walls of the Mavoy, because the principle of Gud Asik should make it as though the walls extend all the way up to the Korah!

ANSWER: TOSFOS (9a, DH she'Ein) explains that we do not apply many of the Halachic principles of structural extension to a Korah on a Mavoy. The reason for this is that a Korah enables one to carry in a Mavoy by serving as a Heker, a recognizable indication that the Mavoy ends at that point. (Even according to the opinion that a Korah enables one to carry in a Mavoy by serving as a Mechitzah, it is also a Heker and not just a Mechitzah.) When the Korah does not rest directly on the walls of the Mavoy, people do not notice it and it does not serve as a Heker. A Tzuras ha'Pesach, in contrast, does not serve as a Heker; rather, it forms a Mechitzah, a partition, which does not have to be readily apparent to onlookers. (RASHASH)