Daf Yomi - Sukkah 31 - Stolen S'chach

If one steals wood and uses it for s'chach, it is valid. One of the reasons for this is because the thief dos not have to return the wood, rather the value of the wood. thisis because there was an injunction issued on anyone who steals something and uses it as part of his house or building that he acquires it and he only owes the original owner the value of the stolen object. The sages were concerned that otherwise (if he would have to return that particular beam) the robbers would not repent and return that which they stole.

A question is asked on our Gemora. Biblically, one does not acquire the stolen object - it is only a Rabbinic decree that the wood does now belong to the theif. If so, how can the robber fulfill his Biblical obligation with something that is not Biblically his?

The Shar Hamelech equates this case with a Gemora in Bava Basra 47b that states if one forces someone to sell something, the sale is considered final and deemed valid. Over here where one is obligated to listen to the Sages, it is as if the thief purchased the wood from the owner and now owes him money for it. It is a completely valid sale even Biblically and hence he will fulfill the obligation of sukkah with that s'chach.