While the Mishna (9a) introduced us to a hulda – a marten – that we suspect may hoard hametz in houses already cleaned for Pesah, on our daf Rava presents us with another small animal, an akhbar. The akhbar discussed is, apparently, a conventional house mouse (Mus musculus), a small rodent that grows up to eight centimeters. This small creature sustains itself by eating food that is left around the house, usually bread crumbs and other such things.
Rava said: If one saw a mouse enter a house with a loaf of bread in its mouth, and he entered after the mouse and found crumbs, the house requires additional searching, due to the fact that a mouse does not typically generate crumbs. Therefore, it cannot be assumed that these crumbs are from the loaf snatched by the mouse.
The Maharam Halavah quotes the Rif as explaining that mice do not make crumbs when they eat, so the crumbs that are found cannot possibly be from the loaf of bread brought in by the mouse, forcing us to check the house a second time. The Ramban understands Rava’s ruling to mean that a mouse usually finishes the crumbs that he makes. According to this reasoning, if the amount of crumbs that is found is the size of the piece that the mouse was carrying, it could not possibly be from the piece that was recently brought in, since the mouse would have finished the crumbs. If, however, only a small amount of crumbs were found, we can rely on the fact that the mouse ate the bread, leaving behind a small amount of crumbs, but the house does not need to be rechecked.
This discussion leads Rava to ask a series of hypothetical questions about this case:
• What if the mouse was seen bringing in a loaf of bread and carrying out a loaf of bread? Do we assume that it is the same loaf, or not?
• If we assume that it is the same loaf, what if we see a mouse carrying in a loaf, and a mouse of a different color carrying out a loaf? Do we still say that it is the same one?
• If we assume it could not be the same loaf because mice do not take from one another, what if a mouse carried in a loaf of bread and a rat is seen carrying out bread? Can we assume that the rat took the loaf from the mouse?
• And what if we see the rat carrying out a mouse and a loaf? Would that prove that it was the same hametz that was carried in?
To all of these questions the Gemara answers Teiku – the question stands.
The Shulhan Arukh declines to bring these cases, with the explanation that they are so unlikely to occur that they do not require a pesak.