Shabbat 106 - Traps
Earlier we learned that for doing destructive acts on Shabbat one is not liable. However, Rabbi Shimon finds two exceptions to this: wounding a person or burning something. Here one is liable for Shabbat violation. Why? After all, Rabbi Shimon is the one who permits unintended violations, such as dragging a bench on the ground, even though he may dig a ditch! Rabbi Shimon will tell you that since the Torah had to allow circumcision on Shabbat, this shows us that normally making a wound is prohibited. Then what about our previous learning that ALL destructive acts are not a Torah violation? - That is the opinion of Rabbi Yehudah. And what is the basis for it? He said that circumcision is a constructive act of rectifying the child.
Trapping an animal constitutes hunting, and that is prohibited on Shabbat. But what is trapping? - If one drives a bird into a cage or a deer into courtyard - in other words, if he makes the animal sufficiently trapped so that he can catch it in one attempt. A swallow bird is an exception: it loves freedom so much that even after being trapped in a small enclosure it will not becomes submissive, but will try to fly away instead. Therefore, a smaller than usual enclosure would make it trapped.
Art: Christian Krohg - Young Woman on a Bench