By: Reb Avi Lebovitz
Rav Hamnuna holds that the exemption of borrowing an animal with its owner only applies to a case where the owner is borrowed to work in the same labor as the animal, AND that the owner was there at the time that the accident occurred.
This approach in שאלה בבעלים is certainly the most rationale, because the reason for the exemption is that since the owner was there at the time of the accident doing the same work, he should have watched his own animal.
This is the approach of the GR"A in Aderes Eliyahu to explain the concept of שאלה בבעלים. However, the Meshech Chochma (Mishpatim 22:3) points out that this approach doesn’t at all work with the halachic ruling, rejecting Rav Hamnuna entirely. We hold that שאלה בבעלים is completely dependent on the time that the object was borrowed, the owner must have already been in the borrower service (or at least begin immediately), AND it makes no difference if the owner is working with the object that has been borrowed or in something else. What then is the rationale behind this halachah?
The Meshech Chochma suggests that the rationale is based on a Gemora in Megillah (26b) which states that the sanctity of a Shul would go away, not only through a sale, but even if it is given as a gift because: if they would not have received any benefit from the recipient, they would not have given it to him (therefore it is like a sale). Here too, it is not common to do such a huge favor for the borrower to lend him an object and work for him at the same time. Therefore, we assume that the owner is only lending and working in exchange for something that he received. Since the owner received something in exchange, the borrower is no longer a borrower, but has been downgraded to a renter, who is exempt if an unavoidable accident occurs.
This approach doesn’t explain those who hold that negligence is also exempt, and it also doesn’t explain why he is exempt for theft according to those who hold a renter is normally liable for theft (like a spaid custodian). Perhaps we will have to assume a “lo p’lug” (no distinction) to explain those opinions.
With this, we can somewhat explain the Gemora’s question (96a) whether שאלה בבעלים applies when the owner sends his messenger rather than going himself. Does the sending of a messenger also indicate that the owner must have received something significant in return for lending and supplying a worker, or do we only assume that when he himself goes? However, if this is in fact the question of the Gemora, it shouldn’t really be dependent on the halachah of שלוחו של אדם כמותו anywhere else; it should be an isolated question regarding the assumption in this specific situation. Yet, the Gemora compares it to the general halachah of שלוחו של אדם כמותו by the annulment of vows.