Sanhedrin 25a: There was a butcher who was caught selling treif meat, so Rav Nachman declared him unreliable and fired him. He went and grew his hair and nails long. Rav Nachman thought that now that he showed signs of repentance, he could reinstate him. But Rava said to him: “Perhaps he is just fooling us.” “So what must he do to show that he has repented?” “He must go to a place where no one knows him [and he doesn’t think he is being observed by the rabbis of his hometown] and return an expensive lost item to its owner, or else slaughter for himself, find the animal treif and discard it although it is expensive.”
סנהדרין כה ע”א: ההוא טבחא דאישתכח דנפקא טריפתא מתותי ידיה, פסליה רב נחמן ועבריה. אזל רבי מזיה וטופריה. סבר רב נחמן לאכשוריה. אמר ליה רבא: דילמא איערומי קא מערים? ־ אלא מאי תקנתיה? כדרב אידי בר אבין. דאמר רב אידי בר אבין: החשוד על הטריפות ־ אין לו תקנה עד שילך למקום שאין מכירין אותו, ויחזיר אבידה בדבר חשוב, או שיוציא טריפה מתחת ידו בדבר חשוב משלו.
A caterer came to Rabbi Yisroel Reisman to apply for a hechsher. Until now, he had been under the supervision of a different rabbi. Rabbi Reisman looked into his history and found that he had once violated Shabbos by turning on the heat under the cholent for a kiddush. He must have forgotten to turn it on before Shabbos, and knowing that everyone was relying on him to supply hot food, he couldn’t withstand the test. Rabbi Reisman asked him about this incident on the interview and he replied, “You’ve never heard of teshuva? I’ll never do it again.” He did not get the hechsher.
Source: Rabbi Reisman, tape on YD 185:1
[This halacha is brought in Yoreh Deah 119:15. The Shach (30) says clearly that even one such offense is enough to disqualify him. The Taz (16), however, quotes an opinion that in our time, since there are so many sinners and it is impossible for rabbis to rectify the problems and enforce the strict law, if the rabbis see fit they may warn him and punish him for the first offense, but let him continue selling.
In another shiur (on YD 69:10), Rabbi Reisman commented that nowadays, if you take away someone’s hechsher, he will just go and find a different kashrus organization that is willing to give him a hechsher.]
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