Mikvaot, Chapter One, Mishnah Eight
Today’s mishnah deals with the two bodies of water that have the highest degree of purity.
1) Superior to them are “smitten waters” which can purify even when flowing [on the ground].
2) Superior to them are “living waters” for in them there is immersion for zavim and sprinkling for metzoraim, and they are valid for the preparation of the hatat waters.
Section one: “Smitten waters” is a term used to refer to a spring whose water has somehow been despoiled. Either the water is salty or it is not cold because it is standing. These waters are purer than the spring whose standing waters have been augmented with drawn water because the water of this spring purifies even when the water is flowing on the ground. However, it still does not count as “living waters” which is the purest form of water. Indeed, “smitten waters” literally could be translated as “killed waters” which is the opposite of “living waters.”
Section two: “Living waters” are fresh water in the spring. This is the level of purity required for the immersion of a zav, a person with an abnormal genital discharge (see Leviticus 15:13).
The metzora is a person who had some sort of skin disease (we learned about this in Negaim; see Leviticus 14).
This is also the type of water required to make the “hatat waters” the waters into which are put the ashes of the red heifer (see Leviticus 19:16; we learned about this in Parah).