Commenting to the beginning of Parashat Metzora, the Midrash (Vayikra Rabba (16:2) famously tells of a peddler who traveled about through several towns announcing that he was selling “life-giving potion.” Rabbi Yannai heard the announcement from the attic where he sat and studied, and he invited the merchant to his home to show him the valuable merchandise that he was advertising. The peddler opened a Sefer Tehillim and pointed to the verses (34:13-15), “Who is the man who desires life, who loves [his] days in which to behold goodness? Guard your tongue from evil, and your lips from speaking deceit…”
Upon seeing the peddler’s “merchandise,” Rabbi Yannai exclaimed, “All my life I have read this verse, but I did not know its meaning, until this peddler came along.” Many writers and darshanim addressed the question of why the admonition to “guard your tongue from evil” is “life-giving potion,” and what new insight into the verse was revealed to Rabbi Yannai by this merchant.
The Klausenberger Rebbe explained that lashon ha-ra, indulging in the dissemination of negative information about other people, blinds a person to his own faults and shortcomings. As long as we focus our attention on the failings of others, we will pay little or no attention to our own failings. And thus the “life-giving potion,” the first, indispensable step we need to take if we seek to live our lives properly, in accordance with God’s will, is “guard your tongue from evil.” We must turn our focus and attention away from the faults of other people and direct our minds inward, towards improving ourselves. This is the deeper meaning of the verses that Rabbi Yannai learned from this merchant. He learned that avoiding negative speech about others is the cure for our blindness, our inability to see our own faults and identify the areas of our behavior that require improvement. Once we cure this ill, we are then in a position to find our other ills and treat them, so we can live the kind of noble and meaningful lives that we are meant to live.