Study Guide Eruvin 37 Today's daf is sponsored by Ellen Golub & Steven Sass in honor of the Bar Mitzvah of their oldest grandson, Levi Moshe Weinograd, on Shabbat Nitzavim-Vayelech. Levi, Bobbe and Zayda love you so much! We offer two words of wisdom: D’kula bo. Ellen & Steve are also celebrating the brit milah of their newest grandchild, Leo Golub-Sass, named for Ellen’s beloved father, Leo Golub, Aryeh Leib Ben Eliyahu z"l. May Leo grow to love the Jewish people as his great-grandfather did and may he become a Talmid chacham.  And by Michelle Winer for a refuah shelaimah for her daughter, Bella Rachel bat Malka Enya. You keep handling each challenge as they come and manage to smile every day. As I learn each day’s daf, I do so with the hope that my and so many other women’s learning will help bring about a refuah shelaimah for you. And also our learning should be a refuah shleima for Netanel Ilan ben Shayna Tzipora.  Should we accept Ayo's braita which had Rabbi Yehuda saying breira, retroactive determination, doesn't work or our mishna saying it works? The gemara grapples with the Tosefta where Rabbi Yehuda holds we cannot use breira in order to support Ayo's reading. Ulla holds otherwise and reads the Tosefta differently. Rabbi Yosi and Rabbi Shimon also appear in the Tosefta regarding tithing wine forbidding it, seemingly because they don't allow breira. However, several other sources are brought which seem to contradict. The gemara reconciles the difficulties from the other sources in various ways. Would those who do not allow breira say that it would apply not only for Torah laws but also for Rabbinic laws?