Q. I traveled to be at my future son-in law's aufruf. When I came to the shul I realized that I did not have my tallis with me. I was unable to ask someone to lend me one, but I found someones weekday tallis. Since I would not have been able to come after Shabbos to fold it as it was, can I use it and fold it back on Shabbos? If this happens to be a rather new tallis with foldings clearly marked, is it also permitted?
A. Poskim disagree if one is permitted to fold a tallis on Shabbos after the end of davening.
Shulchan Aruch (O. H. 302: 2) rules that folding a tallis when not on the original creases is permitted
Mishna Berura (ibid. 19) writes that although later day Poskim agree with the Shulchan Aruch “he who wishes to be more stringent and not fold at all, is certainly better.” Piskei Teshuvos (392 n.102) quotes a list of Poskim that maintain it is better not to folded at all.
However, Horav Shlomo Miller Shlit'a pointed out that the very hetter or permit to use someones tallis without his permission, which is based on the principle of "nicho lei leinish lemeavad mitzva bememonei" or a person is pleased and consents when someone complies with a mitzva, by using his property, is not that clear cut and dry, as a number of limiting issues may be involved.
a) Mekor Chaim and Eishel Avrohom opine that it may not apply to mitzvos that are not obligatory, such as wearing a tallis, since one may well daven without one, and besides he is already complying with the mitzva by using a tallis kotton.
b) Shulchan Aruch (O.H. 14: 4) and many Poskim maintain that the tallis has to be returned in the exact condition one found it, and that may not be always possible or doable. Mishna Berura (ibid. 15) indeed addresses the issue as to what to do on Shabbos. He indeed mentions that on Shabbos, one should return after folding it, but not in its original creases. Then quotes Magen Avraham who is lenient and says he may not folded at all.
c) Aruch Hashulchan (ibid.) and others assert that in our days when hygiene is a great concern, people are more uneasy and uncomfortable when others use their personal items. This especially applies to clothing such as a tallis that people may wear directly over their heads (when sweating). Although, one may reason that maybe only a minority of people would mind, still Shulchan Aruch Horav affirms that we do not follow majority rules when dealing with others money or property. Thus one should assume that the owner of the tallis could be one of the uneasy and disagreeable minority, and using his tallis without permission would constitute an act of stealing. (See Piskei Teshuvos ibid. n.67).
Therefore the Rov recommends that one, visiting another shul on Shabbos, should make every effort to ask someone to lend him a weekday tallis, if he forgot to bring his, and not take one without permission.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit'a