Vayikra 14:35

כנגע 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).

וּבָא֙ אֲשֶׁר־ל֣וֹ הַבַּ֔יִת וְהִגִּ֥יד לַכֹּהֵ֖ן לֵאמֹ֑ר כְּנֶ֕גַע נִרְאָ֥ה לִ֖י בַּבָּֽיִת׃

and he that owns the house shall come and tell the priest, saying, It seems to me there is as it were a plague in the house: