Yevamos, Chapter 8, Mishnah 1. This mishnah deals with the eligibility to eat Terumah of someone who is unable to be circumcised or to become purified, and also with the law of a p'tzua daka and a k'rus shafchah - the men themselves, their wives and their slaves.
"Arel v'chol tamei lo yochlu ba'terumah" - an uncircumcised man and anyone who is tamei may not eat Terumah:
An arel is someone who has not been circumcised. This situation can occur to a Jew even without his sinning by remaining uncircumcised - for someone who deliberately refrains from circumcising himself is an apostate and a heretic, and he has an entirely different set of problems. Here the mishnah is speaking about someone whose brothers died earlier as a result of circumcision, and who therefore may not actually be circumcised, because it would endanger his life (in today's terms: hemophilia).
A kohen who comes to eat Terumah must be circumcised, and he may not be tamei. The mishnah therefore rules that an arel, and likewise anyone who is tamei, may not eat Terumah.
"N'sheihen v'avdeihen yochlu ba'terumah" - their wives and their slaves may eat Terumah:
The wives and slaves of these men - both of the arel and of the one who is tamei - may eat Terumah. The reason is that the disqualification of the arel and of the tamei is purely technical, and has nothing to do with their personal definition and status. The one cannot remove his foreskin, and the other is tamei at this moment and has not yet become tahor.
Their personal status therefore remains that of someone who, technically speaking, would have been able to eat Terumah had he been able to overcome these obstacles. For that reason their wives eat by virtue of being married to them, and their slaves eat by virtue of being their property.
P'tzua daka and k'rus shafchah:
The mishnah continues and deals with a p'tzua daka and a k'rus shafchah, which are blemishes in the male reproductive organs:
P'tzua daka - damage to the testicles.
K'rus shafchah - damage to the male organ itself.
The law in the Torah is that someone who has sustained one of these injuries may not marry a Jewish woman. Nevertheless, they themselves are permitted to eat Terumah, and there is nothing in their blemish that prevents this. Therefore "hen v'avdeihen yochlu" - they and their slaves may eat.
On the other hand, "un'sheihen lo yochlu" - their wives may not eat. Since these women are forbidden to them and cannot marry into the Jewish people through them, they are disqualified from eating Terumah because they had relations with a man who is forbidden to them, and such relations render them a zonah.
"V'im lo yada mishena'asah p'tzua daka uch'rus shafchah - harei eilu yochlu" - and if he did not know her from the time he became a p'tzua daka or a k'rus shafchah, these women may eat:
This is the exception: they were lawfully married, and afterwards the injury occurred to him, and from the time that he became a p'tzua daka or a k'rus shafchah he did not know her - that is, they did not have marital relations from the moment she became forbidden to him. In such a case those wives do eat Terumah, since they were not disqualified, because they never had forbidden relations.
Conversely, a p'tzua daka or k'rus shafchah who was already in this condition and betrothed a woman - even though he has not yet had relations with her, she no longer eats Terumah, because she is "waiting for invalid relations": she is waiting for relations that will disqualify her from Terumah. Any woman in a situation where the next stage after the betrothal is by its very definition forbidden relations does not eat Terumah already at that stage.
In summary: in this mishnah we learned that the arel and the tamei do not eat Terumah, but their wives and slaves do eat, since their disqualification is technical and does not change their personal status. A p'tzua daka and a k'rus shafchah, by contrast, eat, as do their slaves, while their wives are disqualified because of the forbidden relations - unless they had no marital relations from the time he became so. And a woman who was betrothed to him when he was already in this condition does not eat even before the relations, because she is waiting for invalid relations.
In the next mishnah we will deal with the details of p'tzua daka and k'rus shafchah.