Positive Mitzvah Twenty-Four

Ablutions of the Kohanim

Shemot 30:19 From it, Aharon and his sons shall wash their hands together with their feet.

The Kohanim are commanded to wash their hands and feet when they have to enter the Temple or when they are about to perform the service. This is the Mitzvah of the Sanctifying of the Hands and Feet.

He who violates this Positive Mitzvah incurs the penalty of death by the hand of Heaven; that is to say, a Kohen who serves in the Temple without [first] washing his hands and feet becomes liable to that penalty. This rests on His words (Baruch Hu), "When they go into the tent of meeting,] they shall wash with water, that they did not" (Shemot 30:20)

The detailed rules of this Mitzvah are set out in their entirety in the second chapter of Zevachim

Failure to comply with this Mitzvah invalidated the service of any ministering Kohen. Generally, one such ablution prior to engaging in the service of the day was sufficient, so that if the Kohen did not leave the Temple Court or touch any unclean object in the course of the day, he required no further sanctification. But it must be remembered that while the Kohanim were commanded to wash their hands and feet before they could perform any service, not person whatsoever could enter the Temple court (i.e. the Court of the Yisraelim, the Court of the Kohanim, etc.) without having first immersed his whole body in a ritual bath (Yoma 30a) and additional strictures attached to persons who were unclean. Furthermore, in connection with the service of the Kohen Gadol (High Priest) on Yom Kippur (see Pos. Mitzvah 49), the Mishnah informs us:  "On this day the Kohen Gadol immerses himself five times and washes his hands and his feet ten times" (ibid., 30a)