四分律比丘含注戒本 2.557

2.557

時，諸比丘坐起行來，多殺細小諸蟲，或有作波逸提懺者，或有畏慎者，佛言：「不知，不犯。」

(At that time, when many bhikṣus sat, rose, walked, and came, they killed many tiny bugs; some made confession as a prāyaścittika, while others were fearful and scrupulous. The Buddha said: "If one did not know, there is no offense.")