Rashi on Leviticus 14:35/רש"י על ויקרא י״ד:ל״ה

1כנגע נראה לי בבית SOMETHING LIKE A PLAGUE HATH SHOWN ITSELF TO ME IN THE HOUSE — Even if he (the owner of the house) be a learned man and knows for sure that it is a plague he shall not decide the matter as a certainty saying, "a plague hath shown itself to me" but, “something like a plague hath shown itself to me" (Mishnah Negaim 12:5; Sifra, Metzora, Section 5 10).