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.
In addition to the obligations of the shomer ḥinnam, shomrei sakhar are liable if the item is stolen.
Shomrei shakhar are also liable if the item is lost or misplaced, even if the loss was not a result of negligence.
The gemara in tractate Bava Metzia[2] discusses the biblical sourcing of each of the categories of shomrim.
[3] In order for a shomer to verify the circumstances of the entrusted item's loss, shomrim are required to swear a group of oaths in Beit Din.