Reference for Bava Metzia 186:6

דשמע קל אריה ועל אי הכי אומדין אותו מאי הוה ליה למעבד היה לו לקדם ברועים ובמקלות

He raised another objection: If a shepherd, who was guarding his flock, left it and entered the town, and a wolf came and destroyed [a sheep]; or a lion, and tore it to pieces, we do not say, 'Had he been there, he could have saved them;' but estimate his strength: if he could have saved them, he is responsible; if not, he is exempt.<span class="x" onmousemove="('comment',' V. supra 41a. ');">⁵</span>

Jastrow

Jastrow

Jastrow

Jastrow

Jastrow

Jastrow

Jastrow

Jastrow

Jastrow

Jastrow

Jastrow