It is written in Sha’ar Ha’kavanot that the Arizal (Rav Yishak Luria of Safed, 1534-1572) allowed fulfilling the Misva of Arba Minim before sunrise. Normally, a Misva that applies during the daytime may not be done before sunrise, but the Arizal allowed shaking the Lulab any time after Alot Ha’shahar (daybreak), even before sunrise.
It must be noted, however, that the Arizal wrote this only in reference to a very specific case, namely, where a person is praying Shaharit at sunrise and does not have access to a Sukka in the place where he prays. The Arizal maintained that the importance of shaking the Lulab in a Sukka overrides the requirement to shake the Lulab after sunrise, and therefore, if one goes to pray Shaharit at sunrise in a synagogue that does not have a Sukka, he should shake the Lulab in his Sukka before he leaves for the synagogue. The Arizal would agree, however, that if a person prays at sunrise in a synagogue that has a Sukka – as most synagogues today have – he should shake the Lulab in the Sukka after the repetition of the Amida, before Hallel.
Summary: The Misva of Arba Minim may not be fulfilled before sunrise. The only exception to this rule is a case where one is praying at sunrise in a synagogue that does not have a Sukka. In such a case, according to the Arizal, one should shake the Lulab in his Sukka before leaving to the synagogue, even though it is still before sunrise.
