- The source that a Kohen who is an arel is prohibited to eat terumah
The opening Mishnah of the eighth perek states: הערל וכל הטמאים לא יאכלו בתרומה – An arel, which Rashi explains refers to an arel Kohen whose brothers have died because of milah, and Kohanim who are tamei, may not eat terumah, נשיהן ועבדיהן יאכלו בתרומה – but their wives and their servants may eat terumah. Rashi explains that being an arel or tamei does not remove them from the Kehunah but are personal deficiencies which disqualify them from eating terumah, not their wives or servants. The Gemara brings a Baraisa that states: Rebbe Eliezer said: מנין לערל שאין אוכל בתרומה – From where do we know that an arel Kohen does not eat terumah? נאמר "תושב ושכיר" בפסח ונאמר "תושב ושכיר" בתרומה – The words “toshav v’sachir” are said with the korban Pesach and with terumah, to establish a gezeirah shaveh that teaches: Just as “toshav v’sachir” stated with regard to the pesach, is something in which an arel is prohibited, so too the “toshav v’sachir” stated with regard to terumah, is something which an arel is prohibited to. Rebbe Akiva says that the gezeirah shaveh is not needed, for the passuk states: "איש איש" – A man, a man from the offspring of Aharon who is a metzora or a zav shall not eat from the holies, referring to terumah. The repetition of איש is לרבות הערל – to include an arel in the prohibition not to eat terumah.
- The gezeirah shaveh is mufneh
The Gemara brings a Baraisa that states regarding Rebbe Eliezer’s gezeirah shaveh, מופנה – This gezeirah shaveh is mufneh, - free (meaning there are words in the passuk that are superfluous), for if it were not free the gezeirah shaveh could be refuted as follows: What comparison can be made to the pesach, where one is chayav kares for pigul, nossar and eating it while tamei, whereas in the case of terumah that is not so? Therefore, there would be reason to think that only the pesach is prohibited to an arel, not terumah. The Gemara asks, הי מופנה – which expression of “toshav v’sachir” is mufneh, superfluous? Is it the pesach one, the terumah one, or both? The Gemara concludes that it is the “toshav v’sachir” from the passuk of pesach, for if the Torah literally meant that a toshav v’sachir are patur from a korban pesach, how could that be? A toshav, which is an eved nirtza, and a sachir, which is an eved ivri, are full-fledged Jews. Just because they became servants, does not patur them from the pesach. Therefore, the passuk is mufneh to be used for the gezeirah shaveh. Since there are two extra words in the passuk, “toshav v’sachir, it is a גזירה שוה מופנה משני צדדין – a gezeirah shaveh that is free on two sides, which according to all opinions cannot be refuted.
- An onein is permitted to eat terumah
The Gemara suggests that since the gezeirah shaveh is mufneh from both sides, we could learn that just as with regard to a pesach an onein is prohibited to partake in it, so too an onein should be prohibited from terumah? Rebbe Yose bar Chanina said: The passuk states: "וכל זר" – But any zar may not eat of it (i.e. terumah). This passuk is superfluous and teaches: זרות אמרתי לך ולא אנינות – being a zar prohibits one from eating terumah, but not aninus. The Gemara challenges this derashah unsuccessfully.