Responsa su Deuteronomio 22:8

In addition to these dangers with regard to which one should avoid exposing himself, there are also the dangers concerning which one should avoid exposing others. These are based upon the command (Deut. 22:8) to put a parapet around the roof of the house. This verse ends with: "Lo sosim domim b'vesecho," which becomes the key verse in all the later discussions. In the Sifre (ad loc.) this law is extended to similar neglect of safeguards, such as leaving a well uncovered, or leaving a stumbling block in the road. This duty to avoid causing danger to oneself and to others is codified in Maimonides (Hil. Rozeach XI, 4) and Shulchan Aruch, Choshen Mishpot 427.