According to the Torah (Shemot 22:6-12), the level of responsibility for which a shomer (bailee) – someone who accepts responsibility to guard his friend’s object – is liable, depends on the personal gain that the shomer receives. The Mishna on our daf enumerates four types of shomrim and their level of responsibility. They include:
A shomer ḥinam – who does not derive any personal gain or benefit from watching the object. In the event that the shomer ḥinam performs his duty responsibly and the object is lost or stolen, he can take an oath that he guarded it properly and he will be free of any further responsibility (see 22:6-7).
A sho’el – who borrows the object for his own use, without payment. He is responsible for anything that happens to the animal, and will have to pay full restitution to the owner (see 22:13).
A shomer sakhar – who gets paid for watching the object, and
A sokher – who pays rent to use the object. In these last two cases the shomer will be responsible if the object is lost or stolen, but not if an ones – an unexpected accident – takes place. The Torah’s examples of ones are if the animal dies, breaks a leg or is taken captive.
The Gemara tells a number of stories that illustrate these laws. In one of them we hear of a man named bar Adda who was hired to transport animals. When taking them across the gamla (a narrow bridge) in Neresh, one animal pushed another, and it fell into the river and drowned. Rav Pappa ruled that bar Adda was responsible for the death of the animal, and in response to bar Adda’s claim that there was nothing he could have done, Rav Pappa argued that bar Adda was hired for his expertise and he should have taken them across the gamla one by one.
A gamla is a unique type of bridge. Ordinary bridges are well-built structures of wood or stone that are made to support people and animals crossing a river. A gamla is a simple piece of wood that is laid across a narrow river. While people can usually cross a gamla safely, it would be difficult to move animals across such a bridge.