In this essay we will discuss whether one may borrow another's Tefillin, Lulav, or Sefarim without the owner's permission. We will review this topic from the Gemara, Rishonim, Shulchan Aruch and commentaries to a ruling from Rav Aharon Lichtenstein. It should be noted that borrowing without permission is forbidden ("Sho'el Sheloh Mida'at Ganav Havi," see Choshen Mishpat 359:5). The question is whether borrowing mitzva items is considered an exception to this rule because of a presumption that Jews wish to have mitzvot performed with their property ("Nicha Lei L'inish D'tei'avid Mitzva B'mamonei"). (For further discussion of this issue see Rabbbi J. David Bleich, Contemporary Halachic Problems 4:273-315.)
The Gemara on Bava Metzia 29b seems to categorically forbid borrowing even mitzva items without the owner's permission. The Gemara there states as follows: "a borrower is not authorized to lend the object he is borrowing to another, nor may a renter rent his rented Torah scroll to another renter (sublet). This teaches that we do not say "Nicha Leih L'inish D'tei'avid Mitzva B'mamonei," (that a person desires that his property be used for mitzva purposes)."
It seems, though, from Pesachim 4b that sometimes we do say "Nicha Lei L'inish D'tei'avid Mitzva B'mamonei." The Gemara applies this rule to a case where one rented a house immediately prior to Pesach and discovered that the house was not checked for Chametz. The Gemara states that the renter can not claim that he was defrauded ("Mekach Ta'ut"), by the owner's failure to provide a house that was checked for Chametz. The reason given by the Gemara for this ruling is that we assume that people don't mind doing a mitzva (such as checking for Chametz) themselves or paying someone to perform a mitzva.
The Rishonim take different approaches to resolving this apparent contradiction. In the commentary erroneously attributed to the Ritva ("old Ritva") to Baba Metzia 29b, the answer is as follows. The presumption presented in Pesachim 4b is that a person wants to use his money for the purposes of fulfilling a mitzva. In Baba Metzia 29b, the presumption is that people don't want others to perform mitzvot with their property without permission. According to this approach, the prohibition to borrow without permission applies to mitzva items as well. The Nimukei Yosef (Bava Batra 44b in the pages of the Rif s.v. V'rabanan) agrees with this approach.
The authentic Ritva (new Ritva as it is referred to in Yeshivot) presents a different resolution of the contradiction. He explains that there is a presumption that a Jew is pleased to have others use his property for mitzva purpose "as long as it does not involve a serious financial loss." The reason one may not borrow a Sefer Torah without permission, explains the Ritva, is that the owner fears that excessive usage will quickly wear out the Sefer Torah. One may, however, borrow items to perform a mitzva if usage will not cause a considerable financial loss. As examples, the Ritva presents that one may borrow another's Tallit or Tefillin to be used in the synagogue in which they were found, provided that they are returned to the place they are found.
The Rambam (Hilchot Trumot 4:3) seems to agree with the Ritva's lenient approach. The Rambam permits one to go to another's field, take some fruit from the field and designate them as Truma. As long as the owner later approves of this action, the fruit became legitimate Truma. The Kesef Mishna (ad. loc.) explains that when dealing with mitzvot, implied consent is sufficient. Thus, one may borrow a Mitzva item if the usage will not cause a financial or time loss to the owner.
Accordingly, we have seen that there exists a disagreement among the Rishonim as to whether one may borrow Mitzva items without the owner's permission even if no significant monetary loss is involved. The Shulchan Aruch rules leniently in accordance with the view of the Ritva and the Rambam. In Orach Chaim 14:4, the Mechaber and Rama permit one to borrow another's Tallit and Tefillin without the owner's knowledge. Similarly, the Rama (649:5) permits one to borrow someone else's Lulav from day three to day seven of Sukkot, without the owner's consent (on the first day of Sukkot in Israel and the first two days of Sukkot outside of Israel one is required to own the Lulav). The Rama explains that the reason for this leniency is the presumption that "Nicha Lei L'inish L'meibad Mitzva B'mamonei." The Gra (14:4 s.v. Aval) explains that the borrowing is permissible since no significant monetary loss is involved.
There are, however, limitations to this permissive ruling. The Mishna Berura (14:13) cites the Bach and the Magen Avraham that one may only borrow another person's items occasionally; borrowing on a regular basis constitutes a nuisance and one cannot say "Nicha Lei L'inish L'meibad Mitzvah B'mamonei" in such a situation.
The Mishna Berura further limits the allowance to borrow without permission. He writes that one may only borrow the items in the place where he found them. Since the owner may not want the items removed from that place, one may only presume implied consent to use the items in the place where the owner left them.
Interestingly, the Mishna Berura cites the Pri Megadim who rules that if the owner of the items is present one should ask his permission to use the items even if it is for a Mitzva. This is because of the general rule that one should not rely on a "Chazaka" (presumption of human behavior) to assume something, if that matter can be easily verified empirically. This principle is outlined by the Ran (1b in the pages of the Rif to Pesachim, s.v. Garsinan). The Ran states that even though there is a presumption that one would not engage in Shechita unless he is qualified to do so, the Shochet should nevertheless be tested. Similarly, although one renting a home from a Jew on Pesach eve may assume that the owner checked the house for Chametz, nevertheless, if the owner is available one should inquire whether he performed "Bedikat Chametz" on the property.
Borrowing Sefarim - Rama, Mishna Berura, Aruch Hashulchan, and Rav Aharon Lichtenstein
Borrowing Sefarim without the owner's consent is forbidden by the Rama (O.C. 14:4). The Mishna Berura (14:16) explains that it is forbidden to borrow the Sefarim even on an occasional basis without the owner's consent. The concern is that the reader will intensively use the Sefarim and they will eventually be torn and rendered unusable. The Mishna Berura then cites the Pri Megadim who notes that people commonly borrow Siddurim and Machzorim without the owner's consent, but he is unable to formulate a halachic defense for this practice.
The Aruch Hashulchan (14:13) notes that it is permissible to briefly borrow Sefarim from others. He notes (and approves of) the common practice to do. Similarly, he permits borrowing Siddurim and Machzorim without the owner's permission because "most people do not mind this."
Rav Aharon Lichtenstein (quoted in an essay co-authored by this author and Dr. Ari Greenspan in Alon Shevut Kesher Tefutzot no. 1, Chanukah 5743) explained that there is more room to be lenient today. This is because Sefarim are exceedingly more affordable today than they were even relative to the times of the Mishna Berura. Thus, the concern for monetary loss as a result of tearing pages is not significant. Accordingly, in our times one may borrow Sefarim without permission.
Removing Bone Marrow from a Minor Without Consent - Rav Shlomo Zalman Auerbach
A similar, albeit much more serious problem, is whether one may remove bone marrow from a very young child (who is unable to give consent) to save the life of his brother, if the child is the only potential donor. Rav Shlomo Zalman Auerbach (Nishmat Avraham 4: Choshen Mishpat 243:1) advances the idea that perhaps we can rely on implied consent from the child, meaning that eventually the child will be pleased that bone marrow was removed from him to save the life of his brother. This may analogous to the aforementioned Rambam who permits one to remove fruits from another's field to serve as Truma, since the field owner will eventually consent to this action.