[If] Shavuos falls on the eve of the Sabbath, Beis Shammai say: The day of slaughter is after the Sabbath. Beis Hillel say: There is no day of slaughter after the Sabbath. They concur that if it fell on the Sabbath, the day of slaughter is after the Sabbath.  The Kohen Gadol does not don his [special] garments [on that day]; moreover, they are permitted to eulogize and fast, in order not to confirm the view of those who say that Shavuos is always [the day] after the Sabbath.