Preview: In the prayers for Hoshanah Rabbah we describe the willow-whacking practice as a “custom of the prophets.” What are the roots of this custom? Perhaps they originate in the story of “whacking arrows,” in sefer Melachim – a story with many connections to our custom, once you notice them. Plus, how Yeshayahu’s prophecy of “beating swords into ploughshares” may fit in.