四分律比丘含注戒本 2.203

2.203

尼等吉羅。不犯者：教授尼至日未暮便休；除婦女已，為餘人；若船濟處說法，尼自聽者；若與估客夜說法；若尼寺中；若因人請，值說便聽者，開。

For the bhikṣuṇīs and others, it is a duṣkṛta. Non-offences: if he ceases instructing the bhikṣuṇīs before sunset; if, setting aside women, it is for other persons; if he teaches the Dharma at a ferry crossing and bhikṣuṇīs listen on their own; if he teaches the Dharma at night to merchants; if it is within a bhikṣuṇī monastery; or if, upon an invitation by another person, they happen to hear him teaching—these are permitted.