There are threads on the QB about getting smells out of fabrics which should also work for quilts. There is NO WAY I would wash it before it is COMPLETELY finished. I had a top that was really nasty and thought that a gentle rinse in the tub would get the smell out. It did, but it also caused an unbelievable mess. In your case you depend on that little bit of overhang to hold the binding. Washing it unfinished may well (and most likely will) unravel at the edge and you won't have enough of an edge to have a tight bind.