Ohalot, Chapter Thirteen, Mishnah One
Chapter thirteen deals with the size that a hole in a building must be in order for corpse impurity found in a tent to travel to the other side.
1) One who makes a new light hole, its minimum size is that of a hole made by the large drill of the Temple chamber.
2) The remains of a light-hole [the size is] two fingerbreadths high by a thumb-breadth broad.
a) The following is considered the remains of a light-hole: a window that a person had blocked up but had not been able to finish [being blocked up].
3) [A hole] that was bored by water, or by reptiles or eaten away by salt: the minimum size is that of a fist.
a) If he intended to use it, its minimum size is one handbreadth square;
b) For lighting its minimum size is that of a hole made by the drill.
4) The holes in grating or lattice-work may be joined together to form [an opening] the size of a hole made by the drill, according to the opinion of Bet Shammai.
a) Bet Hillel says: unless there is a hole of the size made by the drill in one place.
5) [The above applies] for purposes of allowing the uncleanness to come in or to go out.
a) Rabbi Shimon says: only for allowing the uncleanness to come in; but for allowing the uncleanness to go out [the minimum size] is one handbreadth square.
Section one: When one makes a new light-hole in a house, in order for it to bring impurity to something on the other side, it must be the size of a hole made by the large drill used in the Temple chamber. This drill is referred to also in Kelim 17:12.
Section two: The “remains of a light hole” is a light hole that they began to close up but they didn’t finish closing it up. It needs only be two finger-breadths by a thumb-breadth. The concept behind this halakhah is that once something enters a certain category, it is harder to leave that category than it was to get there in the first place.
Section three: A hole made by a natural cause must be at least the size of a fist. This is larger than the hole made by the drill. See Kelim 17:12.
However, if he intended to use the hole that was created by a natural cause, it takes on the halakhic requirements of a handmade hole, and it depends on what he wants to use it for. If he intends to use it to put his things there, then it must be one handbreadth square. If he intends to use it for lighting, then the size is smallerthe size made by the drill (section one).
Section four: Bet Shammai holds that the small holes made in grating or in lattice-work join together to create the required sized hole to bring impurity from one side to the other side.
Bet Hillel says that there must be one hole that is at least the size of the drill. In other words, the smaller holes are not combined.
Section five: According to the first opinion, the measure of the size of a drill was stated both to allow impurity to enter a house from an adjacent ohel or to allow the impurity to escape from the house to an adjacent ohel.
Rabbi Shimon says that the earlier halakhah concerning a hole the size of the Temple drill was stated only with regard to allowing impurity to enter. When it comes to allowing impurity to escape, there is a different requirementthe hole must be one square handbreadth. This halakhah is also found in 3:6.