Mishnayos Negaim Perek 7 Mishnah 5

ונקצצה טהורה – as it is written (Leviticus 13:46): “He shall be impure as long as the disease is on him,” but not the days that the bright white spot on his skin was on him and it was cut off.

קצצה מתכוין – in the Tosefta (Tractate Negaim, Chapter 3, Halakha 5 ) it is proven that where he cut off all of the bright white spot on the skin and cut off from the flesh that was around it with it, no one disagrees that he doesn’t have eternal purity. For the Rabbis fined him after he had intended to uproot it/tear it out. But where he cut it and left a remainder from it, whatever the amount, everyone does not argue that he has purity through an eruption (i.e., the white eruption which causes the leper to be declared clean), since he left a remnant from it, they did not fine him all that much. What they do disagree about is when he cut off the bright white spot in the skin in an exactly defined manner, like it is, no less and no more.

ר' אליעזר אומר לכשיולד לו נגע אחר ויטהר ממנו וחכמים אומרים עד שתפרח בכולו – And the Halakha is according to the Sages (i.e., until it spreads all over him). Here we do not have the reading of the words of the Sages (as we had in the previous Mishnah): "או עד שתתמעט בהרת מכגריס"/or until his bright white spot on the skin will diminish to less than the size of a split [Cilician] bean, that specifically concerning tearing/plucking out, the signs/tokens of defilement of the first clause [of the Mishnah]: "ונשארה הבהרת"/but the bright white spot in the skin remained. There it belongs to teach [in the Mishnah]: “until it diminishes to less than the size of a split [Cilician] bean,” but here, the entire bright white spot in the skin was cut off.

ואם היתה בראש הערלה ימול – we are not dealing with circumcision at its appropriate time (i.e., eight-days old for a baby boy), for this is a simple matter, now that on Shabbat the prohibition [which if one violates it leads to the punishment] of stoning is suspended; leprosy, which is a mere prohibition, not all the more so, but even circumcision that is not [performed] at its appropriate time, does not supersede the Sabbath, but supersedes the leprosy, for the positive commandment of circumcision comes and supersedes the negative commandment of leprosy, and in this we hold throughout the entire Torah. Every place that you find a positive commandment and a negative commandment, if you are able to fulfill both of them, it is good. But if not, the positive commandment should come and supersede the negative commandment.