Is it permissible to benefit on Shabbat from someone doing melecha such as carrying outside of the techum? Does it make a difference if the person is doing it on purpose or by accident?
Shalom, Thank you for your question. The laws of benefitting from forbidden labor on Shabbat can be found in the Shulchan Aruch, (Orach Haim) 318,1. In general we rule that it if forbidden to benefit from forbidden labor on Shabbat itself, and that one should wait until after Shabbat to benefit from it. However, in the case of carrying items where there is no eruv, there is a major argument between the early Rabbis. This is because in the case of carrying on Shabbat there is no change to the object being carried. As such, some opinions permit using the object even after it was carried in a place with no eruv, and others forbid it. There is then a secondary argument as to whether those who permit it do so only when it was carried by mistake or even when it was done so on purpose. Except in cases of great need, we rule strictly that one should not benefit from such acts. [In the case of things being bought from outside the "tachum" there is additional reason to be strict, as there is a special degree on this act when done by a non-Jew, and this may well apply to a Jew also.] Blessings.