Sforno on Deuteronomy 22:8/ספורנו על דברים כ״ב:ח׳

1ולא תשים דמים בביתך כי יפול הנופל, if it were to happen that someone falls off that roof you could not have been the indirect cause, seeing you had put up a protective railing. Had you not done so, your family might bear part of the guilt for such a mishap.