Chapter 3, Mishna 11, 12 Rabban Yochanan ben Zakkai instituted certain changes in our prayers and rituals as a remembrance of the Holy Temple after its destruction. Who was he? One can only fulfill his obligation to “take the four species” on the first day of Sukkot only with his own lulav and esrog. What do you do if you don’t have one but your friend does? Does a conditional gift transfer legal ownership? Why did Rabban Gamliel spend an exorbitant sum on his lulav and esrog?