Another matter, “this shall be the law of the leper.” That is what is written: “Who is the man who desires life?” (Psalms 34:13). There was an incident involving a certain peddler who would circulate in the towns adjacent to Tzippori and would proclaim and say: ‘Who seeks to purchase the elixir of life?’ [People] would crowd around him. Rabbi Yanai was sitting and interpreting verses in his study.
He heard [the peddler] proclaiming: ‘Who seeks the elixir of life?’ He said to him: ‘Come in here and sell it to me.’ He said to him: ‘You and those like you do not require it.’ [Rabbi Yanai] pressed him and he came to him. [The peddler] took out the book of Psalms and showed him the verse: “Who is the man who desires life?” What is written after it?
“Guard your tongue from evil…Turn away from evil and perform good” (Psalms 34:14–15). Rabbi Yanai said: ‘Solomon, too, proclaims and says: “One who guards his mouth and his tongue guards himself from troubles”’ (Proverbs 21:23). Rabbi Yanai said: ‘All my life I have been reading this verse, but I did not know how obvious it is10That guarding the tongue is the elixir of life. until this peddler came and informed [me]: “Who is the man who desires life.”’
Therefore, Moses cautions Israel and says: “This shall be the law of the leper [hametzora],” the law of the defamer [hamotzi shem ra].