What level of responsibility does someone have when they are holding collateral for a loan?
According to the Mishna (80b) if one person lends money to another and accepts collateral to guarantee the loan, he is considered a shomer sakhar – a paid watchman or bailee – who has a fairly high level of responsibility for the object, i.e. he is liable to pay for the object if it is lost or stolen. Rabbi Yehuda disagrees and distinguishes between lending fruit – where he is, in fact, considered to be a shomer sakhar on the collateral – and lending money – where the lender will be only a shomer hinam – an unpaid watchman – on the collateral.
Our Gemara explains the opinions in the Mishna as follows: According to the first opinion, the sakhar (reward) that the lender receives is sakhar mitzva – the reward for having performed a mitzva by lending money. The Gemara in Bava Kamma (56b) explains this to mean that since at the time of the loan he would be free from giving charity to a poor person, given his involvement in the loan – based on the idea that ha-osek be-mitzva patur min ha-mitzva (someone who is involved in fulfilling a mitzva is free from performing other immediate mitzvot) – he is viewed as having received a tangible benefit and is therefore a shomer sakhar.
Rabbi Yehuda rejects the idea of sakhar mitzva as being significant in this context. Nevertheless, if the lender gave fruit to the borrower he directly benefits from the exchange – since fruit can spoil, by lending the fruits now he will receive fresh fruit later on. If, however, he lent money, if sakhar mitzva is not significant then the lender has received no benefit, and cannot be considered as having received payment. Thus he remains a shomer hinam.