- Three cases where Hillel and Shammai disagree
Rav Huna stated that Hillel and Shammai only argued in three cases:
What’s the minimum amount of flour required that the dough would be subject to the separation of challah?
What’s the minimum amount of drawn water (מים שאובין) that will disqualify a mikveh?
If a woman who becomes a Niddah is retroactively declared tamei from the time of her last examination.
Rav Huna’s list did not include cases where that particular halacha had already been disputed about in previous generations. In addition, Rav Huna only included cases in which Hillel and Shammai never came to an agreement.
- The earth outside of Israel is tamei
One of the decrees of the early Tannaim was that land outside of Eretz Yisrael was to be considered tamei. - גזרו טומאה על ארץ העמים.
The Gemara clarifies the background of this decree:
Yose ben Yoezer, Ish Tzreidah, and Yose ben Yochanon, Ish Yerushalayim decreed that land outside of Eretz Yisrael is considered tamei. Their concern was that since the idolaters did not mark their graves, any place in their lands was suspect of containing a grave. Unmarked graves were also more likely to be plowed over resulting in scattered bone fragments.
Therefore if terumah came in contact with its dirt, the terumah would not be allowed to be eaten. However, the terumah was not allowed to be burned either. In the words of the Gemara, this terumah is “suspended”.
The Rabbonim of eighty years before the destruction of Bayis Sheini later expanded the decree to include it’s airspace as well. They were concerned about the graves imparting tumah via roof tumah to someone passing over it.
Finally in Usha, the Rabbis added a stringency and required burning terumah that came in contact with its dirt. (However, terumah that came in contact with the airspace of ארץ העמים would still remain with its status of being “suspended”).
Decree that glassware is susceptible to tumah
Yose ben Yoezer and Yose ben Yochanan decreed that glassware should be susceptible to tumah. R’ Yochanan said in the name of Reish Lakish that that reason why they enacted this decree, is that since that glassware comes from sand (a type of earth), it should have the same halacha as earthenware, which is susceptible to tumah.