QUESTION: The Gemara cites two statements of Tana d'Vei Rebbi Yishmael which apparently contradict each other. The first Tana d'Vei Rebbi Yishmael says that other materials (in addition to wool and linen) cannot become Tamei with Tum'as Sheratzim. The second Tana d'Vei Rebbi Yishmael says that other materials can become Tamei with Tum'as Sheratzim. Rava resolves the contradiction by saying that both statements of Tana d'Vei Rebbi Yishmael agree that other materials can become Tamei when they are three by three Tefachim large, but not when they are three by three Etzba'os. The first Tana d'Vei Rebbi Yishmael was referring to other materials that are only three by three Etzba'os when he said that other materials cannot become Tamei.

The Gemara points out that Rava, by giving this answer to resolve the two statements of Tana d'Vei Rebbi Yishmael, contradicts an earlier statement that he made. Rava said (26b) that Tana d'Vei Rebbi Yishmael is of the opinion that other materials, even when they are three by three Tefachim, cannot become Tamei.

The Gemara answers that either Rava changed his mind and retracted his earlier statement, or that it was actually Rav Papa, and not Rava, who suggested this resolution of the two statements of Tana d'Vei Rebbi Yishmael. (Since Rav Papa was a student of Rava, the students mistakenly attributed the answer that Rav Papa suggested to his mentor, Rava.)

How can the Gemara say that Rav Papa is the one who gave the resolution that was originally said in the name of Rava, when Rav Papa himself (a line later in the Gemara) gives a completely different resolution? (Rav Papa explains that the first Tana d'Vei Rebbi Yishmael agrees that other materials can become Tamei, and when he said, "Just like there [regarding Tum'as Nega'im] the Torah limits it to wool and linen, so, too, everything is limited to wool and linen," he was not referring to all other Tum'os, but rather, to the laws of Kil'ayim.)

(a) RASHI explains that when the Gemara says that Rav Papa is the one who said this answer, it does not mean that he gave the same answer as the one above that was attributed to Rava. Rather, he gave a different answer to resolve the contradiction between the two statements of Tana d'Vei Rebbi Yishmael; it was not the same answer that was attributed to Rava. The students thought that they heard the answer in the name of Rava, and, furthermore, they misunderstood the answer, misconstruing it to have something to do with Rava's original statement (that he really did say, concerning the opinion of Tana d'Vei Rebbi Yishmael that other materials do not become Tamei).

(b) The RAMBAN suggests that when Rav Papa's own answer (that the first Tana d'Vei Rebbi Yishmael was referring to Kil'ayim) was refuted, he offered a new solution. That second solution was the one that was originally attributed to Rava.

(c) The Ramban offers another approach. Rav Papa's answer does differentiate between other materials that are three by three Tefachim and those that are three by three Etzba'os. The first Tana d'Vei Rebbi Yishmael agrees that other materials can become Tamei when they are three by three Tefachim. However, when he says "so, too, everything is limited to wool and linen," he is stating that just like Nega'im is absolutely limited to wool and linen (and not even large articles made of other materials can become Tamei with Tum'as Nega'im), so, too, there is another Halachah that is absolutely limited. He cannot be referring to other Tum'os, because other Tum'os do apply to other materials when they are three by three Tefachim. It must be that he is referring to some other Halachah that does not apply at all to other materials. Rav Papa explains, therefore, that the words "so, too, everything is limited to wool and linen" must be referring to Kil'ayim, and that is what is similar to Nega'im.

Accordingly, Rav Papa actually said both ideas -- that other materials can become Tamei with Tum'as Sheratzim when they are three by three Tefachim, and that the first statement of Tana d'Vei Rebbi Yishmael was referring only to Kil'ayim.

QUESTION: The Mishnah states that products of a tree cannot become Tamei with Tum'as Ohel.

How can the Mishnah say that Tum'as Ohel does not apply to products of a tree? The Gemara (17a) explicitly states that a Marde'a (a wooden stick) can become Tamei with Tum'as Ohel if it hovers over a Mes!

(a) TOSFOS (DH v'Ein Metamei) answers that tree products remain Tahor when they are made into an Ohel while they are attached to the ground. Pishtan is the only tree product that can become Tamei even while it is attached to the ground.

(b) The RASHBA suggests that all materials, even Pishtan, are Tahor when attached to the ground. When not attached to the ground, all materials that pass over a dead body become Tamei. The Mishnah is referring to a piece of wood that was set up for permanent use as a tent, but was not attached to the ground. In such a case, only Pishtan can become Tamei.

(c) The TOSFOS HA'ROSH explains that the Mishnah is discussing an object that is still in the process of being made. If, while making the object, one decides to use it as an Ohel, it is no longer considered a Kli and it will not become Tamei. Pishtan, on the other hand, remains a Kli even if one decides, while processing it, that it will be used only as an Ohel (and not as a utensil or article of clothing). It does not lose its status of a Kli and it will still become Tamei.