Tying knots: professional, unprofessional, and knots that won't last. The Gemara says: well, obviously (!) a woman is permitted to knot her robe, and goes on to explain why it's a specified case. Especially because of knots that are not permanent, yet remain in place... permanently. Also: Halitzah. Plus: Rabbi Yochanan, Rabbi Yehudah, and Hizkiah on the impurity of vessels and how repairs change the original. A bit of Who's Who, including the generational shift from Tannaim to Amoraim, and the diminishment from one generation to the next. Which all provides the context for the story about the donkeys who wouldn't eat from untithed food.