A brief review, then we learn that Rabbi Yehoshua ben Besairah is the author of the teaching (that the Baal Musaf of Shmini Atzeres begins saying ‘Mashiv Haruach’) of both our Braisa and a just introduced, second Braisa; it’s voluntary to praise G-d for dew, because dew is never withheld, and how do we know?  From Elijah and Ahab.