Musar for Nedarim 123:3
רבי חמא בר רבי חנינא איקלע לההוא אתרא בזמן שהוקפלו רוב המקצועות הוה קאכיל יהיב לשמעיה לא אכיל אמר ליה אכול כך אמר לי רבי ישמעאל בר רבי יוסי משום אביו הוקפלו רוב המקצועות מותרות משום גזל ופטורות מן המעשר
R. Tarfon was found by a man eating [of the figs] when most of the knives had been folded, [whereupon] he threw him into a sack and carried him, to cast him in the river. 'Woe to Tarfon,' he cried out, 'whom this man is about to murder!' When the man heard this,<span class="x" onmousemove="('comment',' That he was R. Tarfon. ');"><sup>3</sup></span> he abandoned him and fled. R. Abbahu said on the authority of R. Hananiah b. Gamaliel: All his lifetime that pious man grieved over this, saying. 'Woe is me that I made [profane] use of the crown of the Torah!'<span class="x" onmousemove="('comment',' I.e., over saving his life by revealing his identity. ');"><sup>4</sup></span>