In Jewish religious law (halacha), a shomer (Hebrew: שומר, pl. שומרים, shomrim) is a Jewish legal guardian entrusted with the custody and care of another's object.
The laws of shomrim (pl. "keepers"; "watchmen") are derived from the Torah in the Book of Exodus (Shemot 22:6-14). It is also discussed in the Talmud in the Bava Kamma and Bava Metzia tractates, which deal with torts, usury, and property law.
There are four types of shomrim: [1] an unpaid custodian, a paid custodian, a borrower, and a renter (shomer ḥinnam, shomer sakhar, shoel, and sokher, respectively). Each shomer has distinct laws in halacha that apply to it. The two major factors that determine a guardian's liability are whether the guardian has the ability to use the item (i.e., a renter or borrower) and whether money is exchanged. In general, having the ability to use the item and being a paid custodian increase the guardian's liability, while paying for the use of something (i.e., being a renter) decreases the guardian's liability.