Bava Kamma 30A

משום רבי ישמעאל כו׳!

in the name of R' Yishmael that one is liable to pay for damage caused by a pit that he dug in the public domain, even if it is not his personal property?

לא קשיא; הא דידיה. הא דרביה.

The Talmud answers: This is not difficult. This ruling, that he is exempt, is his own opinion, whereas that ruling, that he is liable, is the opinion of his teacher R' Yishmael, and he disagrees with it.

מתני׳ השופך מים ברשות הרבים, והוזק בהן אחר ⁠– חייב בנזקו. המצניע את הקוץ ואת הזכוכית; והגודר את גדרו בקוצים; וגדר שנפל לרשות הרבים; והוזקו בהן אחרים ⁠– חייב בנזקן.

Mishnah: In the case of one who pours water in the public domain, and another person incurred damage due to it, the one who poured water is liable to pay for his damage. In the case of one who conceals a thorn or a piece of glass in his wall adjacent to the public domain, or one who puts up a fence of thorns, or one who puts up a fence that subsequently fell into the public domain, and others incurred damage due to any of these, he is liable to pay for their damage.

גמ׳ אמר רב: לא שנו אלא דנטנפו כליו במים, אבל הוא עצמו ⁠– פטור; קרקע עולם הזיקתו.

Talmud: With regard to the case of one who pours water in the public domain, Rav says: They taught that he is liable only when the clothes of one who slipped were soiled by the dirty water, but if the one who slipped himself was injured, the one who poured the water is exempt, as it is the impact with the ground that injured him, not the water.

אמר ליה רב הונא לרב: לא יהא אלא כרפשו!

Rav Huna said to Rav: Why should he be exempt from paying restitution for the injury? Even if the water that he poured is considered only like his filth that he tossed in the public domain, he should be liable. Since the muddy ground caused the injury, and the mud belongs to him, as it results from the addition of his water to the dirt, he should be liable.