Negaim, Chapter Thirteen, Mishnah Eleven
1) If a metzora entered a house all the vessels in it, even up to the roof beams, become unclean.
a) Rabbi Shimon says: only up to a height of four cubits.
2) Vessels become unclean immediately.
a) Rabbi Judah says: only if the metzora stayed there as much time as is required for the lighting of a lamp.
Section one: A “metzora” is a person who has a nega. If he/she should enter a house, all of the vessels in the house are defiled.
According to the first opinion, this includes even vessels that are placed high in the house, close to the roof beams.
Rabbi Shimon says that the impurity only reaches as high as the height of an average person when he stretches his hands up. This is estimated to be 4 cubits (about 2 meters high). Above that is another domain and therefore any vessels found close to the roof beams remain pure.
Section two: According to the first opinion, as soon as a metzora enters a house, he immediately defiles all of the vessels therein.
Rabbi Judah says that he must remain there the time that it takes to light a lamp. According to the Tosefta this only refers to a metzora who enters his friend’s house without permission. In such a case, the vessels there are impure only if he stays long enough to light a lamp (at which point his friend, if he was there could tell him to leave?). But if a metzora enters his own house, or someone else’s with permission, the vessels are defiled immediately.