Although there is a mitzva of simha – joyous celebration – on all of the pilgrimage holidays – the shalosh regalim – there is a unique emphasis on this aspect of the holiday on Sukkot. In order to fulfill this mitzva, a number of special activities were instituted in The Temple: more music was played, a system of unusual torches was lit up, and the physical set-up of the grounds of the mikdash was changed to accommodate the large number of revelers in a safe and protected manner. The fifth perek of Massekhet Sukka, which begins on our daf, focuses on these matters.
The first Mishna teaches the rule of the halil – the flute played during these festivities – which could not be used as part of the celebrations on Shabbat or Yom Tov. (Although the Mishna mentions the halil specifically, there was an entire orchestra of instruments. The halil is focused on because, according to the Rambam, it was the most important instrument, or because, according to the Bartenura, it was the one that was heard most clearly.)
It was stated that Rav Yehuda and Rav Eina disagreed: One of them teaches that the celebration was called the Celebration of Drawing [sho’eva] and one of them teaches that it was called the significant [hashuva] celebration. Mar Zutra said: The one who taught sho’eva is not mistaken, and the one who taught hashuva is not mistaken. The one who taught sho’eva is not mistaken, as it is written: “And you shall draw [ushavtem] water with joy from the wells of salvation” (Yeshayahu 12:3), and its name reflects the fact that it is a celebration of the water libation. And the one who taught hashuva is not mistaken, as Rav Nahman said: It is a significant mitzva and it originated from the six days of Creation.
This difficult statement is explained by Rashi as referring to the shittin, which, as we learned on the last daf, are thought to have existed since the time of creation. Others suggest that this is connected with a midrash that describes how disturbed the lower waters were when they were separated from the upper waters on the second day of creation (see Bereshit 1:6-8). According to the midrash, God promises them that they will be raised up to similar heights through the water libation, which is why nisukh ha-mayim is related to the creation of the world.