Halocho #171 - Why do we shake the Lulav?

On Sukkoth there's a Mitzva to shake the four species; a Lulav, 3 Haddasim, 2 Aravot and an Etrog. The Torah commands us to shake the four species on all 7 days of Sukkoth in the Bet Hamikdash (Holy Temple), and on the first day of Sukkoth everywhere else. After the Bet Hamikdash was destroyed, the Rabbis instituted shaking the four species during the entire Sukkoth, Zecher L'Mikdash; in memory of the Temple. One does not shake the four species on Shabbat. The Lulav is a palm branch that is still closed. Once the leaves start fanning out, it's no longer a Lulav. A Lulav has a spine from which the leaves protrude; this spine needs to be facing you when you shake the four species. The Lulav spine should be straight, a slight curvature towards you is allowed. The Lulav spine must be at least 4 Tefachim (32 cm - 13") long. This is measured from the bottom of the lowest "leaf" to the bottom of the highest "leaf". Each "leaf" is made of 2 parts that are connected (and will eventually open up into a V-shaped palm leaf). If these double-leaves start separating then the Lulav may no longer be Kosher. Special care should be taken that the highest leaves remain coupled. Source: Shulchan Aruch 645. Ktiva Vechatima Tova; wishing you a year with lots of time to learn Torah, - Danny Sunday, 14 Elul 5768