LEVITICUS 23:40

On the first day you shall take the product of hadar trees, branches of palm trees, boughs of leafy trees, and willows of the brook, and you shall rejoice before Hashem your God seven days. LEVITICUS 23:40 (The Israel Bible™)

Hoshana Rabbah is the seventh day of the festival of Sukkot. The word ‘Hoshana’ refers to a series of seven prayers in which we call to Hashem to redeem His children and provide us with sufficient rain during the upcoming rainy season in Israel. Today, all seven Hoshana prayers are recited in synagogues as worshipers circle the sanctuary with their four species (used for worship during the festival of Sukkot) in hand. When the seven processions around the sanctuary are complete, a special ritual is performed in which the willow branches are struck against the floor of the synagogue by worshipers. This ritual symbolizes the worshipers desires to rid themselves of any remaining sins after Yom Kippur and make themselves worthy of receiving bountiful rain in the coming months.