In the times of the Talmud a certain merchant who sold all kinds of herbs and medicines lived near the town of Zippori. Everyday he walked through the streets calling out, "Whoever wants to live a long life, come and buy this special potion!"

Of course, wherever he went people poured from their homes to see what this magical potion could be which would give them long life. Once, the great Sage, Rabbi Yannai came to see what the man was selling, for he, too, wanted long life. "No, Rabbi, you, who devote your whole life to studying the Torah, don't need this medicine."

But Rabbi Yannai was insistent. The salesman took from his bag a book of Psalms and handed it to the rabbi. "Is this the potion which offers long life?" the Sage asked.

The merchant opened the book and pointed to the words, "Who is the man who wants life? Guard your tongue from speaking evil." The merchant explained, "I teach this sentence to all the people who come to buy my medicine."

Rabbi Yannai was impressed by the merchant's explanation. "You are very correct," he said, "this is truly the potion of long life! Now I understand this teaching which King David implanted in his Psalms, for when we refrain from maligning others, G-d will grant us long life.

King Solomon, the wisest of men said, 'He who guards his mouth and tongue, guards his soul from evil.' You are selling the best possible 'medicine,' and I bless you that you will have lots of success in your work!"