Bechoros Daf 12 בכורות דַף 12

The next Mishnah states that one may not redeem a פטר חמור with a calf, a חיה, a shechted animal, a tereifah, כלאים, or a כוי. Rebbe Eliezer allows using כלאים. In a Baraisa, בן בג בג derives these restrictions from a gezeirah shavah ("שה שה") from korban pesach. Several cases are considered for using as a redemption שה: (1) May one redeem with a בן פקועה (fetus found in a shechted animal)? According to the Rabbonon, that it may be eaten without shechitah, is it considered כבישרא בדיקולא – like meat in a basket (and considered “a shechted animal), or כיון דהשתא מיהא רהיט ואזיל – since now it is alive and running about, it is considered a "שה"? Amoraim debate this issue. (2) One may not redeem with a נדמה – an animal which resembles a different species from its parents, according to the opinion which disqualifies כלאים. (3) One may not redeem with פסולי המוקדשין – disqualified korbanos, because the Torah compares them to צבי ואיל – a deer and a hart, which cannot redeem a פטר חמור. (4) בהמת שביעית – an animal purchased with produce grown during shemittah cannot redeem a definite פטר חמור, because it is forbidden as סחורה – using the shemittah animal for business. However, it can redeem a ספק פטר חמור.

The Mishnah concluded that if the owner gave the פטר חמור to the Kohen without redeeming it, אין הכהן רשאי לקיימו עד שיפריש שה תחתיו – the Kohen is not allowed to keep it at all unless he separates a sheep in its place to redeem it. This accords with a Baraisa teaching that if a Yisroel has a פטר חמור in his house, and the Kohen says תנהו לי ואני אפדהו – “Give it to me, and I will redeem it,” the owner may not give it to him אלא אם כן פדאו בפניו – unless [the Kohen] redeems it in his presence.

Rabbah bar Avuha said: זאת אומרת נחשדו הכהנים על פטרי חמורים – this is to say that Kohanim are suspected regarding firstborn donkeys, that they might use them before redeeming them. Without Rabbah bar Avuha’s statement, one might have thought this suspicion only applies היכא דמחזק לן דמיקרי – where we have established that [this specific Kohen] is considered suspect, but an ordinary Kohen is not suspected to use it before redeeming it. Therefore, he taught that all Kohanim are suspected, דמורה בה היתירא – because he may rationalize that it is permissible for him to use it before redeeming it, since the שה will be his anyway.

The next Mishnah states: המפריש פדיון פטר חמור ומת – if one designated a lamb for redemption for a firstborn donkey and [the lamb] died before being given to a Kohen, Rebbe Eliezer says חייבין באחריותו – he is responsible for [the lamb], כחמש סלעים של בן – like one is responsible to replace the five selaim used to redeem his firstborn son if they were lost before the Kohen received them. This is based on a hekesh with בכור אדם. The Chochomim say he is not responsible for the lamb, just as he is not responsible for replacing lost redemption money of maaser sheni. Rebbe Yehoshua and Rebbe Tzadok testified that the Kohen has no claim at all in such a case. If the donkey died before the lamb was given to the Kohen, Rebbe Eliezer says יקבר – it should be buried, and the lamb remains permitted to the Yisroel owner, since he holds the redemption is only completed when the Kohen receives the שה. The Chochomim say the donkey need not be buried, and the lamb is given to the Kohen.