Commentary for Parah 9:8

מי חטאת שנפסלו – as for example, that their appearance changed not on account of themselves, and in a similar manner , from the things that invalidate the waters of purification/expiation.

Hatat waters that have been invalidated [still] defile one who is clean for terumah [by contact] with his hands or with his body. And one who is clean for the hatat they defile neither [by contact] with his hands nor [by contact] with his body. Hatat waters that have been invalidated (for instance, because the person did some sort of work after preparing them) still convey some degree of impurity. They defile a person who has immersed in a mikveh with the intent of eating terumah, either by contact with his hands or by contact with his body. However, they don't defile someone with regards to non-sacred produce; meaning one who wants to eat non-sacred produce and has had contact with disqualified hatat waters does not defile the produce. Note that regular hatat waters do convey impurity. If someone is ritually clean enough to perform the red cow ritual, then disqualified hatat waters don't defile him at all. He can still perform the ritual even after contact with him.

מטמאין את – the person (see also Tractate Kelim, Chapter 1, Mishnayot 1-2).

If they become unclean, they defile one who is clean for terumah [by contact either] with his hands or with his body, And one who is clean for the hatat they defile [by contact] with his hands but not [by contact] with his body. Hatat waters that have been defiled convey impurity to one who is pure enough to eat terumah in the same way as do disqualified hatat waters. The one difference between disqualified and impure hatat waters is that the latter do defile a person clean enough to perform the red cow ritual by virtue of contact with his hands. However, if they have contact with his body, he remains pure.

הטהור לתרומה – whether he touched them with his hands or whether he touched them with his body, they are considered like suitable/appropriate like waters of expiation/purification, and this defilement is from the Rabbis, for from the Torah, since they were made unfit/invalid, their greater defilement spread all over/blossomed, and because of this, it (i.e., the Mishnah text) teaches that “it renders unclean the person who is clean for heave-offering,” which implies especially for heave-offering but not for non-holy offerings.

ואת הטהור לחטאת לא בידיו – that is to say, it does not defile the pure person for a sin/purification offering whether he touched them with his hands or whether he touched them with his body, for the they are considered appropriate/suitable like the waters of purification/expiation, and these that one carries the waters of expiation that have in them [enough] in order for sprinkling or he touches them, he is impure for all things, but for a sin-offering/expiation, however, he is pure.

נטמאו מטמאין את הטהור לתורמה – like the waters of suitable/acceptable sin-offerings/expiation offerings, but a person who is clean for the purification offering, it defiles him if he touched it with his hands, for since they were defiled, they are not worse than the rest of the impure foods and liquids that defile the hands, for we hold that the purification of the waters of purification/sin-offering, when his hands were defiled/made unclean, his body was made unclean.