כל ימי הסגיר אתו. וְלֹא יָמִים שֶׁקָּלַף אֶת נִגְעוֹ; יָכוֹל שֶׁאֲנִי מוֹצִיא הַמֻּחְלָט שֶׁקָּלַף אֶת נִגְעוֹ, תַּ"ל כָּל יְמֵי: 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).
יטמא עד הערב. מְלַמֵּד שֶׁאֵין מְטַמֵּא בְגָדִים; יָכוֹל אֲפִלוּ שָׁהָה בִכְדֵי אֲכִילַת פְּרָס, תַּ"ל וְהָאוֹכֵל בַּבַּיִת יְכַבֵּס אֶת בְּגָדָיו, אֵין לִי אֶלָּא אוֹכֵל, שׁוֹכֵב מִנַּיִן? תַּ"ל וְהַשּׁוֹכֵב, אֵין לִי אֶלָּא אוֹכֵל וְשׁוֹכֵב, לֹא אוֹכֵל וְלֹא שׁוֹכֵב מִנַּיִן? תַּ"ל יכבס יכבס רִבָּה; אִם כֵּן לָמָּה נֶאֱמַר אוֹכֵל וְשׁוֹכֵב? לִתֵּן שִׁעוּר לַשּׁוֹכֵב כְּדֵי אֲכִילַת פְּרָס (שם): יטמא עד הערב [AND HE THAT COMES INTO THE HOUSE] SHALL BE UNCLEAN UNTIL THE EVENING — This tells us that merely going into the house does not render his garments unclean (since it does not state, as in the next verse, that he shall wash his garments) (Sifra, Metzora, Chapter 5 5). I might think that his garments do not become unclean even if, after coming into the house, he remained there long enough to eat a half-loaf (an ordinary meal, equal in mass to 4 eggs)! It, however, states, (v. 47) "And he that eateth in the house shall wash his garments", for we may reason as follows: I have here only the law regarding one who actually eats. Whence may I derive that this applies also to one who sleeps in the house? Because Scripture states "and he who sleeps [shall wash his garments]". Now I have only the law regarding one who eats and regarding one who sleeps in the house; whence may I derive that the same law applies to one who neither eats nor sleeps (but merely stays in the house)? Because it states יכבס יכבס (twice) in v. 47 where it could have written: והשכב והאכל בבית יכבס את בגדיו, and such wording would imply that only those who actually sleep and eat in the house must wash their garments. By the insertion of the first יכבס we have two coordinated sentences of similar import and this suggests that sleeping and eating are merely examples of cases where garments would require washing. Thus the use of the first יכבס serves to include besides one who sleeps and one who eats in the house anyone who stays there. If this be so (i. e. if it means that the garments of anyone who stays in the house become unclean) why does it expressly mention one who eats and one who sleeps? Let it merely state: one who stays in the house shall wash his garments, when these also would be included! But this is done in order to designate for him who sleeps in the house (i. e. who does anything in the house beyond entering and immediately leaving it, as is mentioned in v. 46) a minimum period of time the stay during which renders his garments unclean, viz., a time long enough to eat a half-loaf (cf. Sifra, Metzora, Chapter 5 7-8).