Deuteronomy 22:8

Thou shalt make a battlement A fence or breast-work, because the roofs of their houses were made flat, that men might walk on them. Blood The guilt of blood, by a man's fall from the top of thy house, through thy neglect of this necessary provision. The Jews say, that by the equity of this law, they are obliged, and so are we, to fence or remove every thing whereby life may be endangered, as wells, or bridges, lest if any perish through the omission, their blood be required at the hands of those who have neglected to perform so plain a duty.