Related for Niddah 99:10
ת"ל (ויקרא יג, ב) והובא אל אהרן הכהן או אל אחד מבניו הכהנים הא למדת שאפילו כהן אחד רואה את הנגעים
leprosies are further compared to controversies: As controversies are not to be tried by relatives, so are leprosies not to be examined by relatives. In case [one were to argue:] 'As controversies must be tried by three men so must leprosies also be examined by three men, this being logically arrived at a minori ad majus: If controversies affecting one's wealth must be tried by three men, how much more so matters affecting one's body', it was explicitly stated, When he shall be brought unto Aaron the priest or unto one of his sons the priests.<span class="x" onmousemove="('comment',' Lev. XIII, 2 emphasis on 'Aaron' and 'one'. ');"><sup>9</sup></span>