四分律比丘含注戒本 2.313

2.313

(If one does not have a reason for eating as a dissentient group, one should stand up and announce, 'I have no reason for this meal as a dissentient group; I wish to seek to leave.' If others have no reason, they are also permitted to leave. If there are two or three persons, they may eat at will. If four persons or more, they should divide into two groups and take turns entering to eat. If one has a reason for a dissentient group and wishes to enter, one immediately stands up and announces, 'I have a reason for a meal as a dissentient group; I wish to seek to enter.' The Buddha said: 'One should enter according to seniority of elder monks.' If having a reason one does not state it, it is a duṣkṛta. Conforming to eating as a dissentient group, with each swallow a falling [offence] is incurred. Bhikṣuṇīs share the offence. As for non-offences: the exceptions listed in detail above; if there are two or three persons; eating in turns; or if having stated that one has a reason, one leaves—these are permitted.)