If a ritually-clean person was standing inside a nega-infected house and he reached outside with rings on his hands, then if he remained long enough to eat half a loaf, the rings are rendered unclean. If he was standing outside and reached inside with rings on his hands, Rabbi Yehuda says that they’re rendered unclean immediately but the Sages say they are only rendered unclean once he remains there long enough to eat half a loaf. The Sages said to Rabbi Yehuda, “If when his entire body is unclean he doesn’t render things on him unclean until he remains long enough to eat half a loaf, then doesn’t it make sense when his entire body isn’t unclean that he doesn’t render things on him unclean until he remains there long enough to eat half a loaf?”
If a metzora (a person with tzaraas – colloquially a “leper” but not really) enters a house, all the utensils in it are rendered unclean, all the way up to the rafters; Rabbi Shimon says they are only rendered unclean up to a height of four cubits (about six feet). Utensils are rendered unclean immediately; Rabbi Yehuda says the utensils are only rendered unclean if the metzora remains there long enough to light a lamp.