Bechoros Daf 9 בכורות דַף 9

The next Mishnah states: חמורה שלא ביכרה – regarding a female donkey which had not previously given birth, וילדה שני זכרים – and gave birth to two males, he gives one lamb to the Kohen, because one of them is a bechor. If it gave birth to a male and female (and it is unknown which was born first), מפריש טלה אחד לעצמו – he separates one lamb to redeem the male in case it is a bechor, but keeps the lamb for himself, because a redeeming lamb is permitted in benefit, and the Kohen must prove that it belongs to him. If two female donkeys which never gave birth gave birth to two males between them, they are both redeemed. If there is one female, he gives one lamb to the Kohen, and if there are two females, the Kohen receives nothing (Rashi adds that he separates two lambs and keeps them). If one female donkey had previously given birth, and another had not, and both gave birth to males, the Kohen receives one lamb, but if a male and female were born, he separates one lamb and keeps it.

Rebbe Yirmiyah says that the above Mishnah does not agree with Rebbe Yose HaGlili, who holds אפשר לצמצם – it is possible to be exact, meaning that both births can occur at exactly the same moment. He holds that when twin firstborn sheep are born simultaneously, both are bechoros and both are given to a Kohen. Accordingly, he holds that if both donkeys appeared to be born at the same moment, the owner would have to redeem both. Abaye disagrees and says that Rebbe Yose HaGlili’s opinion is limited to twin kosher bechoros, where the passuk says "הזכרים לה'" – the “males” (plural) are to Hashem, and the "ה" excludes firstborn donkeys from this law. However, a Baraisa explicitly teaches that Rebbe Yose HaGlili holds that twin firstborn donkeys are both bechoros, refuting Abaye. Although the passuk teaching that multiple firstborns are considered bechoros is written about kosher animals, Rebbe Yose HaGlili derives that the same rule applies to donkeys.

The Mishnah taught that a safek פטר חמור is redeemed with a lamb, which the owner keeps. This redemption is necessary to remove its prohibition, which proves that a פטר חמור is forbidden in benefit before it is redeemed. This follows Rebbe Yehudah’s opinion, whereas Rebbe Shimon permits benefiting from a פטר חמור before redemption. Rebbe Yehudah’s reasoning is explained: יש לך דבר שהקפידה עליו תורה לאפקועי לאיסוריה בשה – is there anything which the Torah insisted that its prohibition is removed specifically with a שה that it permitted before being redeemed? [Although  a פטר חמור can be redeemed with anything equaling its full value, a שה can redeem it regardless of its value.] This specificity of requiring a שה for פדיון indicates that פדיון removes a prohibition. Rebbe Shimon holds: יש לך דבר שפדיונו מותר והוא אסור – is there anything whose redemption is permitted in benefit, while [the redeemed item] was forbidden? Since the שה is permitted for benefit (even after redeeming the פטר חמור), the donkey must also have been permitted for benefit. Alternatively, Rebbe Shimon darshens a passuk to permit a פטר חמור in benefit. Rebbe Yehudah darshens it differently, leaving a פטר חמור forbidden in benefit, like a kosher bechor.