Yerushalmi Yevamot 4:16 ירושלמי יבמות ד׳:ט״ז

MISHNAH: If his wife died, her sister is permitted to him. If he divorced her and she died, her sister is permitted to him²²⁸Lev. 18:18. If she was his wife for one minute, her sister is forbidden to him during her lifetime, by biblical standards. The same holds for the sister-in-law from a childless brother by rabbinic standards.. If she had married another man and died, her sister is permitted to him. If his sister-in-law died, her sister is permitted to him. If he performed ḥalîṣah with her and she died, her sister is permitted to him.

HALAKHAH: “If his wife died, her sister is permitted to him,” etc. That means, her mother is forbidden to him²²⁹The prohibition of the sister is the only incest prohibition lifted after the death of the wife.. Did not Rebbi Jacob bar Aḥa say in the name of Rebbi Eleazar: If a woman waiting for her levir died, her mother is permitted to him²³⁰Since there was only candidacy and that becomes void with the death of the sister-in-law; Halakhot 2:1, 4:8, Soṭa2:5.. But since we stated: “If he performed ḥalîṣah with her and she died, her sister is permitted to him,” therefore he stated “her sister²³¹Since rabbinically, all close relatives of the sister-in-law except the sister remain forbidden..”