Chullin Daf 129 צולין דַף 129

The Gemara discusses a כזית of meat cut off from an אבר מן החי with the intent to use it as food (for non-Jews). As food, it contracts tumah from the אבר מן החי, provided that it first undergoes הכשר for tumah. Although it was previously metamei with טומאה חמורה – severe tumah as [part of an] אבר מן החי, and should presumably not require הכשר, Rava explains: כששימש מעשה עץ שימש – when it served as part of something that was metamei with טומאה חמורה, it served the function of wood, not food. Therefore, when it later assumes the status as food requires הכשר like any other food. The Gemara proceeds to answer five additional questions with this principle. For example, כופת שאור שיחדה לישיבה – a block of leaven which one designated for sitting loses its status as חמץ (and may be kept on Pesach), and becomes a seat susceptible to the טומאה חמורה of מושב. This tumah may be דאורייתא, yet is not an example of food transmitting טומאה חמורה, because the leaven is serving as a מעשה עץ (i.e., a seat), not as food.

In the Mishnah on Daf 127b, Rebbe Meir said that after an animal dies, its formerly dangling flesh requires הכשר before it can become tamei, while the dangling אבר is metamei as an אבר מן החי. The Mishnah concludes that Rebbe Shimon rules “it” tahor, and after extensive discussion, the Gemara concludes that Rebbe Shimon is referring to the בשר (the אבר, however, is tamei as אבר מן החי). Rebbe Yochanan explains that Rebbe Shimon infers from the passuk "מכל האוכל אשר יאכל" – from any foods which can be eaten: אוכל שאתה יכול להאכילו לאחרים קרוי אוכל – food which you may feed to others (i.e., non-Jews) is called “food,” but אוכל שאי אתה יכול להאכילו לאחרים אין קרוי אוכל – food which you may not feed to others is not called “food” regarding tumah of food. Since בשר מן החי is forbidden even to gentiles, it cannot contract טומאת אוכלין.

In the Mishnah on Daf 127b, Rebbe Meir said that after an animal dies, its formerly dangling flesh requires הכשר before it can become tamei, while the dangling אבר is metamei as an אבר מן החי. The Mishnah concludes that Rebbe Shimon rules “it” tahor, and after extensive discussion, the Gemara concludes that Rebbe Shimon is referring to the בשר (the אבר, however, is tamei as אבר מן החי). Rebbe Yochanan explains that Rebbe Shimon infers from the passuk "מכל האוכל אשר יאכל" – from any foods which can be eaten: אוכל שאתה יכול להאכילו לאחרים קרוי אוכל – food which you may feed to others (i.e., non-Jews) is called “food,” but אוכל שאי אתה יכול להאכילו לאחרים אין קרוי אוכל – food which you may not feed to others is not called “food” regarding tumah of food. Since בשר מן החי is forbidden even to gentiles, it cannot contract טומאת אוכלין.