Ohalot, Chapter Ten, Mishnah Three
1) If part of the uncleanness is in the house and part directly [below] the hatchway, the house becomes unclean, and what is directly [above] the uncleanness becomes unclean, the words of Meir.
2) Rabbi Judah says: the house becomes unclean but what is directly [above] the uncleanness remains clean.
3) Rabbi Yose says: if there is sufficient of the uncleanness for it to be divided so that [one part] defiles the house and [the other part] defiles what is directly [above] the uncleanness, [both spaces] become unclean; if not, the house becomes unclean but what is directly [above] the uncleanness remains clean.
Section one: In today’s mishnah there is a source of impurity that is partially underneath the house and partially under a hatchway which is less than one square handbreadth (as in yesterday’s mishnah). According to Rabbi Meir, the house is impure and anything above the impurity is also impure. Rabbi Meir says that the part of the impurity that is in the house joins with the part that is under the hatchway as if all of the impurity was under the hatchway. Therefore, anything that overshadows this impurity is defiled.
Section two: Rabbi Judah disagrees and says that the piece in the house does not join with the piece under the hatchway, for impurity in an ohel (the part in the house) does not join with impurity found under a hole (the hatchway) that is less than one handbreadth.
Section three: Rabbi Yose seems to mediate between the first two opinions. If there is enough impurity to defile both the house and the space under the hatchway, then both are defiled even if there is not enough impurity under each one to defile it. For instance, if there is a piece of impurity the size of two olives (double the amount necessary) and 1 1/2 of it is found under the house and 1/2 under the hatchway, both are defiled.
But if there is not sufficient to defile both, the house is still unclean but the hatchway is clean.