Question (to Hillel ha'Zaken): What can we do for people who did not bring their knives with them [to the Azarah before Shabbos, for Shechitas Korban Pesach]?

Hillel: I heard this and forgot it. Leave it to Yisrael to find a solution. If they are not Nevi'im, they are Bnei Nevi'im (people training to be prophets)!

Immediately, everyone whose Pesach was a lamb, he inserted [the knife] in the wool. [If his Korban was] a goat, he inserted it in the horns. It turned out that the Pesachim brought the knives with them.

Once [Hillel] saw this, he remembered the Halachah. He told them "so I heard from Shemayah and Avtalyon.''

(R. Ze'ira citing R. Elazar): Any Torah that one did not receive on tradition, it is not Torah.

(Mishnah): If one rode [on a Parah Adumah], leaned on it, hung from it, crossed the river through [following] it (he held its tail), folded the rein [and put it] on it or put his Talis on it, it is Pasul.

This (Parah) is learned from that (Pesach), and that is learned from this.

This is learned from that, that if he hung the knife [that will be used to slaughter Parah Adumah] from it, it is Kosher (what is needed for it is not considered Avodah);

And that is learned from this, that any Avodah for the sake of Kodshim (e.g. he spread his Talis over it to protect it from flies) is not considered Avodah [it is permitted with Kodshim].

Implied question: [Before Hillel remembered,] he should have permitted them through a Cholah!

Answer #1: This is like R. Ami [who did not allow making Cholah in order to bring a Milah knife].

Answer #2: You can even say that it is like R. Simon. Just like he forgot this (that one may insert the knife in the wool or the horns), so he forgot this [Heter through Cholah].

(R. Avin): You cannot have two Shavu'os (i.e. 14 years) in which the 14th (Erev Pesach) does not fall on Shabbos! (People should have remembered that Pesach overrides Shabbos!) Why was this Halachah forgotten? It was in order to give greatness to Hillel. (They needed to ask him, and afterwards made him the Nasi.)