399. A Sprinkle a Day: The obligation to carry out the laws of the sprinkling water

The ashes of the red heifer (see Mitzvah #397) were mixed with spring water collected in a vessel at its source. This mixture was called “mei niddah” – “sprinkling water” – because it was sprinkled on those affected by corpse impurity. (The word niddah here has nothing to do with a menstruant woman.) We are commanded to observe the special law of ritual impurity here, namely that the mei niddah renders an unclean person ritually clean but simultaneously renders a clean person unclean.

As we mentioned in Mitzvah #397, this is the great unexplained mystery of the parah adumah. Accordingly, we cannot begin to guess at the reason underlying this mitzvah.

This mitzvah applies to men and women in Temple times. In the Mishna, it is discussed in the eleventh chapter of tractate Parah. It is codified in the Mishneh Torah in the fifth chapter of Hilchos Parah Adumah. This mitzvah is #108 of the 248 positive mitzvos in the Rambam’s Sefer HaMitzvos.