四分律比丘含注戒本 2.481

2.481

(If one does not avoid it, it is a duṣkṛta. Going from a low place to a high place, from a road to an off-road place, if one does not see it, it is a duṣkṛta; an expedient not to see it is also thus; if one sees it, one commits the falling offense. Those who do not commit an offense: if one goes on business; if one is invited and goes; if one is taken away by force; if one walked ahead previously and the army arrived behind, and one leaves the road to avoid it. If water or land routes are cut off, or if there is the danger of wild beasts or bandits, or the water swells greatly, or if one is bound by force, or if there is danger to life, brahmacarya, etc., and one does not leave the road, there is no offense.)