Zevachim 20 - Kohanim Washing their Hands and Feet

Every Kohen has to sanctify  his hands and feet by  washing them from a special large Temple vessel in the morning. Otherwise, his service is invalid.

Rav Assi could not understand the difference between this washing and the ten washings of the High Priest on Yom Kippur, which accompany his five changes of garments - since they do not invalidate the service. Rabbi Yochanan explained to him that the phrase " and then don them " tells us that the garments are essential, but washing is not. Rav Assi's face lit up. But his joy was premature, because Rabbi Yochanan then said, "and by the same token the morning washing should not be significant."

Even if a Kohen was offering animal limbs on the Altar all night, Rabbi Yehudah the Prince says that he needs to wash them again at dawn, but Rabbi Elazar the son of Rabbi Shimon says that he does not need to repeat the washing even if he serves for ten days in a row.

If a Kohen steps out of the Temple, does he need to repeat the washing on return, because he took his mind off the service, or does he not, because he can choose to return any time? No decision is reached.

Art: Mattia Preti - Pilate Washing his Hands 1663