פירוש על טהרות 7:8

מי שהיה טהור – a Kohen who was ritually pure to consume heave-offering and his mind was diverted/he was discarding from his mind to consume any more heave-offering.

One who was clean and had given up the thought of eating [pure food]: Rabbi Judah says that it remains clean, since it is usual for unclean persons to keep away from it. But the sages say that it is deemed unclean. The person described here is someone who usually eats his food while the food is pure (as he is). Then he decides to no longer eat in a state of purity. Rabbi Judah says that the food remains pure because people have grown accustomed to staying away from his food because they know that he wants it to be pure. The other sages disagree and say that once he decides to no longer eat pure food, we can't be sure that he preserved the purity of this food and it must be assumed to be impure.

שדרך טמאים פרושים ממנו – the ritually impure people that know of him that he is ritually pure, separate from him, therefore, we are not concerned that he came in contact with a ritually impure person and he defiled him.

If his hands were clean and he had given up the thought of eating [pure food], even though he says, "I know that my hands have not become unclean," his hands are unclean, since the hands are always busy. Once the person decides to no longer eat his food in a state of purity, he can't really be trusted to keep his hands pure. Hands are "busy" they constantly touch things. Therefore, even if he thinks he preserved their purity, his hands are unclean.

וחכמים מטמאין – for after his mind was diverted/he was discarding from his mind [to consume any more heave offering]. And the Halakha is according to the Sages.

היו ידיו טהורות – in this Rabbi Yehuda agrees that even if he said: “I know that I was my hands were not ritually defiled.”

ידיו טמאות – and they ritually defile the heave-offering, for after he diverted his mind/discarded from his mind to eat [any more heave-offering], because the hands are busy/preoccupied and they touched [impure things] unintentionally.