Continuing its discussion of the laws of muktze, the Mishna teaches:
All vessels that may be moved on, their shards may be moved along with them, as long as they are suited for some purpose. Shards of a large bowl may be used to cover the mouth of a barrel. Shards of a glass vessel may be used to cover the mouth of a cruse.
Rabbi Yehuda says: As long as they are suited for a purpose similar to their original use. Shards of a large bowl must be suited to pour soup into them, and shards of a glass vessel must be suited to pour oil into them.
The Sages of the Jerusalem Talmud asked: Why doesn’t the Gemara state that a shard of glass can be utilized to cut something, just as is stated in the Mishna, which deals with the laws of carrying from domain to domain? They offer two answers: The first is that the Gemara is discussing a shard of glass that is not sharp enough to cut something. The second is that there is a distinction in size between an object large enough to be considered significant with regard to the prohibited labor of carrying out on the one hand, and a smaller size which is sufficient to remove an object from the category of set-aside [muktze].
The difference of opinion in the Mishna is explained by the Gemara as dependent on how the shards of a vessel are perceived. The Gemara explains:
Rav Yehuda said that Shmuel said: This dispute in the Mishna is only with regard to a case where the vessels broke on, as this Sage, the Rabbis, holds it was prepared before as part of the original vessel, and this Sage, Rabbi Yehuda, holds that it is an item that came into being on. Since they were not shards before, they are a new entity and are set-aside. However, if they were broken from before the onset of Shabbat everyone agrees that it is permitted to move them, since they were prepared to serve some function while it was still day, before the onset of.