Kommentar zu Wajikra 13:54

את אשר בו הנגע THAT WHEREIN THE PLAGUE IS — One might think that he has to wash only that spot in which is the plague and not the garment itself! It. however, states: Not, “he shall wash the plague, but “that where in the plague is”. If this be so, then one might think that the entire garment requires washing! It, however, states, (v. 55) הנגע “the plague” (after the plague has been washed), and not the garment. How shall it be done? He washes some of the garment with it (the plague) (Sifra, Tazria Parashat Nega'im, Chapter 15 5).

The place of the eruption alone. Meaning: [You might think] only the place of the eruption is required to be washed but not the garment in which there is the eruption. [Therefore] the verse says: “the article having the eruption...”

The verse says: “the eruption.” Meaning: Later in this section it is written regarding the washing of an eruption (v. 56): “And behold! The eruption grew faint after it was washed,” which refers to the eruption. Meaning: We cannot say the place of the eruption alone, since it says, “the article having the eruption,” and we cannot say the entire garment, because it should say “they shall wash [it]” [and not mention the eruption]. Would we not know that the eruption is in the garment? (Gur Aryeh).