From To Kill a Mockingbird:
I'm not sure why there is no comma in front of "which." She gave Jem only one biscuit-and-butter, so I would have expected a comma there. The which-clause doesn't identify the biscuit-and-butter in any way, in my opinion — there is just nothing to identify. It just says what Jem did to it.Calpurnia seemed to know all about it. She was a less than satisfactory source of palliation, but she did give Jem a hot biscuit-and-butter which he tore in half and shared with me.