(Exodus 12:2) "The beginning of the months": We are hereby apprised that Nissan is the beginning for the months. And whence do we derive (the same for) the reign of kings? From (I Kings 6:1) "In the fourth year of Solomon's reign over Israel, in the month of Ziv (Iyyar), the second month," (his reign having begun with the first month, Nissan). And whence do we derive (the same for) festivals (i.e., that one is not in transgression of delaying his vows until three consecutive festivals have passed)? From (Devarim 16:16) "… the festival of matzoth (in Nissan), and the festival of Shavuot (the Festival of Weeks)h, and the festival of Succoth." We find, then, that Nissan is the beginning for months, for kings, and for festivals.