Shabbat 14a and Shabbat 14b, where we get into the 18 decrees Beit Shammai convinced Beit Hillel to make in the attic of Hananiah b. Hizkiya b. Garon, who was in the process of proving the book of Yehezkel deserved to be in Tanakh. Most of these are about tumah and taharah, ways Hazal worked to protect the idea of terumah needing to be kept ritually pure.
