Commentaire sur Le Lévitique 14:46

כל ימי הסגיר אתו [AND HE THAT COMES INTO THE HOUSE] ALL THE DAYS THAT IT IS SHUT UP [SHALL BE UNCLEAN UNTIL THE EVENING] — "the days that it is shut up", but not during the days in which he had scraped the plague-spot (for through the scraping the uncleanness has, at least for the time being, departed, and the house is only closed again for investigation). I might think that I may also exclude from this law the house that is decidedly unclean through a recurring plague and which must be demolished from which one has scraped the plague-spot (but which has not yet been demolished, for we might assume that for the time being the uncleanness is departed)! It, however, states, "all the days" (Sifra, Metzora, Chapter 5 4).

והבא אל הבית, “anyone who comes to the house, etc.,” a house which has been sealed provisionally does not confer impurity on everyone who enters it. This is why the Torah uses the expression הבא אליו“who enters,” i.e. if the person enters through the regular doorway. If such a person remains inside long enough to eat half a loaf of bread he and his clothing and any other items he carries or wears are defiled through his stay. If his stay is of shorter duration only his person becomes impure as a result of his entering.

[But] not the days in which he scraped. Meaning: All the days of confinement perforce the impurity is there, and therefore a person who enters is impure. However, the days [after] he removes the stones, scrapes, and plasters do not cause impurity to a person who enters since the impurity is gone, until he begins to count the weeks of confinement. This raises a difficulty: Why would you think that a [house that has been] declared [unclean] would be lenient, and a person who enters it would not become impure? [A house that has been] declared [unclean] is more severe than a confined [house], as it says in Toras Kohanim and the Mishnah (Negaim, 13:4): “A confined house causes impurity from the inside and a declared [unclean house causes impurity] from the inside and from the outside”! It appears to me the answer is: Only when the stones upon which the eruption returned are in the wall does it cause impurity, even from the outside. However, if he scraped the stones even though the house stands to be dismantled [I might think] it will not cause impurity to a person who enters during the intermediate days. Therefore, it lets us know: “Any of the days...” (Nachalas Yaakov).