Rabbi Elazar says: it has no proper guarding except the knife. As it was taught, Rabbi Natan says: from where do we learn that a person should not raise a vicious dog inside his house, nor set up a shaky ladder inside his house? As it is said, "You shall not bring bloodguilt upon your house" (Deuteronomy 22:8). "And its owner did not guard it" this comes to include an unpaid bailee. "And its owner did not guard it" as is fitting for it. From here they said: if he guarded it as is fitting he is exempt; if not as is fitting he is liable. "And it killed a man or a woman" Scripture equated a woman to a man.
Keep No Vicious Dog or Broken Ladder in Your Home
Yalkut Shimoni on Torah 340:3
רַבִּי אֶלְעָזָר אוֹמֵר, אֵין לוֹ שְׁמִירָה אֶלָּא סַכִּין. כִּדְתַּנְיָא, רַבִּי נָתָן אוֹמֵר, מִנַּיִן שֶׁלֹּא יְגַדֵּל אָדָם כֶּלֶב רַע בְּתוֹךְ בֵּיתוֹ, וְאַל יַעֲמִיד סֻלָּם רָעוּעַ בְּתוֹךְ בֵּיתוֹ. שֶׁנֶּאֱמַר (דברים כב, ח) "וְלֹא תָשִׂים דָּמִים בְּבֵיתֶךָ". וְלֹא יִשְׁמְרֶנּוּ, לְהָבִיא שׁוֹמֵר חִנָּם. וְלֹא יִשְׁמְרֶנּוּ, כָּרָאוּי לוֹ. מִכָּאן אָמְרוּ, שְׁמָרוֹ כָּרָאוּי פָּטוּר, שֶׁלֹּא כָּרָאוּי חַיָּב. וְהֵמִית אִישׁ אוֹ אִשָּׁה, הִשְׁוָה הַכָּתוּב אִשָּׁה לְאִיש.