Sukkah 44B

כאן במקדש ⁠— כאן בגבולין.

Here, where R' Yoḥanan said that it is a halakha transmitted to Moses from Sinai, he is referring to the mitzva of the willow branch in the Temple; there, where he said that it was established by the prophets, he was referring to the taking of the willow branch in the outlying areas.

אמר רבי אמי: ערבה צריכה שיעור, ואינה ניטלת אלא בפני עצמה, ואין אדם יוצא ידי חובתו בערבה שבלולב. כיון דאמר מר אינה ניטלת אלא בפני עצמה, פשיטא דאין אדם יוצא בערבה שבלולב!

§ R' Ami said: The willow branch taken to fulfill the mitzva requires a certain measure, and it is taken only in and of itself and not with the lulav, and a person does not fulfill his obligation with the willow branch that is bound with the lulav. The Talmud asks: Since the Master said: It is taken only in and of itself, it is obvious that a person does not fulfill his obligation with the willow branch that is bound with the lulav. Why are both statements necessary?

מהו דתימא: הני מילי היכא דלא אגבהיה והדר אגבהיה, אבל אגבהיה והדר אגבהיה ⁠— אימא לא, קא משמע לן. ורב חסדא אמר רבי יצחק: אדם יוצא ידי חובתו בערבה שבלולב (ביום טוב הראשון של חג).

The Talmud answers: It is necessary lest you say that this applies only to a case where he did not lift the willow branch bound with the lulav and then lift it again to fulfill the mitzva of the willow branch; however, in a case where he lifted the lulav and then lifted it again, say no, he fulfills his obligation with the willow branch in the lulav. Therefore, he teaches us that even if one takes the 4 species a second time with the express intent of fulfilling the mitzva of the willow branch, he did not fulfill his obligation, as he must take the willow branch by itself. And Rav Ḥisda said that R' Yitzḥak said: A person fulfills his obligation with the willow branch that is bound with the lulav on the 1st day of the festival of Sukkot.