Pesahim 11a and Pesahim 11b, when R. Yehudah and the Sages do or don’t make protective rules to stop people from violating prohibitions, both when people are being involved with prohibited materials, or they have a monetary stake in the outcome. Then, new Mishnah, about how good we are about knowing the hours of the day, and how that affects the process of separating from hametz on the 14th of Nisan.
