פירוש על פרה 6:4

נתן ידו או רגלו [under running water] – behold that the spouting forth/continuous flow descends rapidly from the curve, but it doesn’t descend into the jar when he wants to fill it for mixing [with the ashes], but if he placed his hands above at the tope of the mountain to make it like a kind of spout/duct in order that the waters would pass through his hand to the jar of mixing of waters and ashes. And similarly, the vegetable greens which are appropriate for eating and are susceptible to receiving ritual defilement.

Introduction Our mishnah teaches that if one causes water to pass from a spring into a jar by using a conduit that is receptive to impurity, the water is invalid. The water must either be filled straight into the jar, or at least go through or over something that does not receive impurity.

פסולים – the waters [are invalid]. As we derived in the second chapter of [Tractate] Zevakhim (folio 25b) from what is written (Leviticus 11:36): “[However, a spring or cistern] in which water is collected shall be pure, [but whoever touches such a carcass in it shall be impure],” they will be through purity (i.e., in their original status), and even though that this Scriptural verse is written concerning a Mikveh/ritual bath, we derive from it all the possibilities. And this is the implication of the Scriptural verse, that will be with all the waters that purify, that through purity it will be, whether one brings them to become a Mikveh or the filling of water that will be through something that is not susceptible to receive ritual defilement.

If he placed his hand or his foot or leaves of vegetables in such a manner as to enable the water to run into a jar, the water is invalid. Hands, feet and leaves of vegetables are susceptible to impurity. Therefore, the water that has passed over them has been invalidated.

If he used leaves of reeds or leaves of nuts the water is valid. However, leaves of reeds or nuts are not susceptible to impurity, therefore, the water remains valid for use.

This is the general rule: [water passing over] that which is susceptible to uncleanness is invalid, but [water passing over] that which is not susceptible to uncleanness is valid. This is the general rule that explains the distinction between section one and two.