四分律比丘含注戒本 2.643

2.643

尼同犯。不犯者：若不知；若屋一切覆，無四障，或半障，或少障；或一切障，無覆、半覆、少覆；或半覆障、少覆障、露地。若病，被繫者，命、梵難，無犯。

(Bhikṣuṇīs commit the same offence. As for the non-offences: if one does not know; if the building is fully covered without four screens, or half-screened, or minimally screened; or fully screened without cover, half-covered, or minimally covered; or half-covered and screened, minimally covered and screened, or in the open ground. If one is sick, detained, or there is danger to life or brahmacarya, there is no offence.)