Shabbat 136B

אם אשת ישראל היא ⁠— חולצת. אם אשת כהן היא ⁠— אינה חולצת.

If she is the wife of an Israelite, meaning she became betrothed to an Israelite, who may marry a woman who has undergone ḥalitza, she performs ḥalitza due to uncertainty. Given that the child may have been stillborn and therefore never considered alive, in which case she would be obligated to undergo levirate marriage or perform ḥalitza, by performing ḥalitza, she removes any doubt and can remain with her new husband. However, if she is the wife of a priest, she does not perform ḥalitza, as if she were to perform ḥalitza she would be prohibited to her husband the priest. Since there are those who hold that that the baby is considered alive from the moment of its birth, based on that opinion, she is exempt from performing ḥalitza, after the fact.

ורב שרביא משמיה דרבא אמר: אחת זו ואחת זו ⁠— חולצת.

Rav Sherevya said in the name of Rava: Both this, the woman married to an Israelite, and that, the woman married to a priest, perform ḥalitza, as the prohibition against marrying a woman not released from her bond of levirate marriage is a stringent one, and the fact that her husband is a priest is not taken into consideration.

אמר ליה רבינא לרב שרביא: באורתא אמר רבא הכי, לצפרא הדר ביה. אמר ליה שריתוה? יהא רעוא דתשרו תרבא.

Ravina said to Rav Sherevya: In the evening Rava indeed said so, as you said; however, in the morning he retracted his statement, and that is what I cited. Rav Sherevya, however, did not accept this explanation, and said: Did you permit the wife of a priest without ḥalitza, despite the fact that Rabban Shimon ben Gamliel deems the baby stillborn unless he survives to the age of 30 days? Since you have violated his ruling, may it be God’s will that you continue along this path and permit the eating of forbidden fat.