Memory and Identity in Ancient Judaism and Early Christianity,
Tom Thatcher ed., SBL, 2014, page 118
An essay by Dr Steven D. Fraade, professor of the History of Judaism at Yale, alerts us to the role of images and iconography in memorialising both loss and continuity in early Jewish history.
The Sifra and the Mishnah both record that in Second Temple times, the lulav - the palm frond, myrtle and willow bundle - and the etrog, a citron fruit, were only taken up and waved on the first day of the feast of Sukkot to fulfill the command: "On the first day you shall take ... and you shall rejoice before the L-rd your G-d seven days" (Vayikra/Leviticus 23:40). However, after the Second Temple was destroyed - by the Romans, the Hurban in 70 CE - instead of dropping the custom,
Rabban Yochanan ben Zakkai made a run that in the provinces the lulav should be taken for seven days, as a memorial to the temple (Sifra Emor 16.9)
As long as the temple stood, Fraade explains, the lulav was taken on the first day for a literal fulfillment, and the seven days days rejoicing took place in the temple before the L-rd. Once the temple was destroyed, however, when coming up to Jerusalem to celebrate thefeast was no longer possible, taking the lulav for seven days "as a memorial of the temple" allowed the presence of the L-rd to be in the provinces as well. Fraade explains:
It should be noted that centuries later, in the iconography of the synagogue, the etrog and lulav commonly appear with ritual objects associated with the temple: holy ark, menorah, shofar and incense shovel. The association of the lulav with the temple did not cease with the latter's destruction but rather continued, with the visual representation of the lulav (among other ritual objects) preserving the memory and symbolic presence of the temple among synagogue worshipers, wherever they might be.