פירוש על פרה 11:1

צלוחית – [a flask with a wide belly and a narrow neck] of water of purification.

A flask that one has left uncovered and on returning found it to be covered, is invalid. If he left the flask uncovered and he came back and found it covered, the water is invalid, lest the person who covered it was not pure in order to perform the hatat ritual.

ובא ומצאה מכוסה פסולה – that I say that a person entered to there and covered it, most people are not ritually pure for the purification offering.

If one left it covered and on returning found it to be uncovered, it is invalid if a weasel could have drunk from it or, according to the words of Rabban Gamaliel, a snake, or if it was possible for dew to fall into it in the night. If he left it covered and then found it uncovered, it is invalid if there is any possibility that a weasel or snake (according to Rabban Gamaliel) drank from it. As we saw in 9:3, these animals backwash into the water, thereby invalidating them. The water is also invalid if there is a chance that dew fell in (see 9:1).

אם יכולה חולדה לשתות ממנה פסולה – but if it (i.e., the weasel) is not able to drink we do not invalidate it for the reason that perhaps an unclean/impure man entered and uncovered it, for it is not the manner of people to uncover but rather to cover because of the insects, but insects/moving creature, it is their manner to uncover/reveal but it is not their manner to cover. But specifically, something covered and he found it uncovered, we are concerned for a weasel, but something that is uncovered and he found it uncovered like he left it, we are not concerned, even though they were suspect to supply revealed/uncovered water, for danger is more stringent than a prohibition.

The hatat waters are not protected by a tightly fitting cover; But water that had not yet been mixed with the ashes is protected by a tightly fitting cover. This section refers to an earthenware jar of hatat waters left in a tent with a corpse in it. Generally speaking if the jar has a tightly fitting lid, it protects its contents from impurity. However, we have seen a special law with regard to the hatat waters they must be in a place of purity. Since he put them in a place of "impurity" the waters are invalid, even if they are pure. However, if the jar contains water that has not yet been mixed with the ashes, it is protected from impurity (see also 10:5). The prohibition against leaving in an impure place refers only to the mixed waters.

או נחש לדברי רבן גמליאל – who said above (in Tractate Parah, Chapter 9, Mishnah 3) that even the snake invalidates it because it vomits.

החטאת – the ashes of the purification rite or the mixed waters [with ashes] that were in the tent of a corpse within a vessel that has upon it a tight-fitting lid.

אינן נצולין – and are defiled. From what is written (Numbers 19:9): “[A man who is pure shall gather up the ashes of the cow] and deposit them outside the camp in a pure place,” but this is not a pure/clean place. But vessels that stand to place in them the waters of purification or the ashes of purification/sin-offering, and similarly the hyssop that is prepared to sprinkle on it, are protected by a tight-fitting lid.