Menachot 37 - February 17, 30 Shvat

There are three different ways that Tannaim derive the source for wearing tefillin on the left hand. However, left-handed people wear them on the right. There are three different ways that Tannaim derive the source for wearing tefillin shel yad on the upper part of the arm. There are two different ways that Tannaim derive the source for wearing tefillin shel rosh on the top of the head. There is a Tannatic debate between Rabbi Yishmael and the rabbis about whether each tzitzit is a distinct mitzva (Rabbi Yishmael), or if one cannot fulfill the mitzva without having tzitzit on all four corners. The Gemara brings three practical ramifications of their debate. There are three examples brought of changes one can make to a four-cornered garment which, while it may no longer look like a four-cornered garment, would still be obligated in tzitzit. Shmuel ruled like Rabbi Yishmael, but the Gemara states that the halakha is not like that and brings a story with Mar bar Rav Ashi and Ravina to prove it.