"And you shall guard this day": What is the intent of this? Is it not already written (16) "all labor shall not be done in them"? This tells me only of labor per se. Whence do I derive (the same for) shvuth (i.e., violation of "resting")? From "And you shall guard this day."—But then let (violations of) shvuth be forbidden on chol hamoed , too! And this would follow a fortiori, viz.: Since the first and the last day (of Pesach (Passover)) are called "a calling of holiness," and chol hamoed is called "a calling of holiness," and (violations of shvuth are forbidden on the first and the last day, let them, likewise, be forbidden on chol hamoed . It is, therefore, written (Leviticus 23:39) "The first day is shabbat (the Sabbath)on (like "shvuth"), and the eighth day is shabbaton" (but not chol hamoed ).