Only a priest was empowered to declare a person, article of clothing, or house afflicted with spiritual leprosy—tzara'at or free of it.
The Torah specifically requires the priests to judge cases of tzara’at because they are the spiritual heirs of the very first priest, Aaron, who was famous for promoting brotherly love among the Jewish people. Because of their love for their fellow Jews, the priests—while taking care not to bend the law of the Torah in any way—will make absolutely sure that the law indeed requires them to pronounce the sufferer defiled before doing so. And if the priests do have to declare a person defiled, they will do whatever it takes to declare him undefiled at the earliest possible opportunity.
Similarly, when we encounter someone who appears to be afflicted with some negative character trait, we should not rush to reject him. Rather, we should first examine ourselves, in order to determine how well we exemplify the ideals of brotherly love. If we are in any way lacking in this regard, we have no right to pass judgment on others, for it could well be that our perception is skewed by our unrefined feelings.
By learning from Aaron how to love our fellows regardless of their objective behavior, we counteract the cause of our present exile, unwarranted hatred. This will hasten the final, Messianic Redemption.
—from Daily Wisdom #1