Reference for Bava Metzia 186:8
ועד כמה עד כדי דמיהן והיכן מצינו בשומר שכר שחייב באונסין דהדר שקיל דמיהן מבעל הבית
— It means that he heard the voice of a lion, and so entered. If so, why judge his strength? What could he then have done? — He should have met it with [the assistance of other] shepherds and staves. If so, why particularly a paid bailee? The same applies even to an unpaid one. For you yourself, Master, did say: If an unpaid bailee could have met [the destroyer, e.g., a lion] with other shepherds and staves, but did not, he is responsible! — An unpaid bailee [must obtain their help only when he can procure them] gratuitously; whereas a paid bailee must even [engage them] for payment. And to what extent?<span class="x" onmousemove="('comment',' Is he bound to hire helpers? ');"><sup>7</sup></span>