The
characteristic common to all of the damagers mentioned in the Mishnah
is that it is their way to cause damage and that the owner is
responsible for watching them.
However, when the words "common characteristic" appear in the Mishnah, this is meant to include something else. What is it?
Abaye
said: "One's stone, knife or burden that he left on top of his roof and
they fell down and did damage." Wind makes this case different.
Rava
said: "An object that was left in the public domain (pit category),
rolled to another place by the feet of the passerby and damaged there."
