四分律行事鈔資持記 1.443

1.443

第三。人非中。亦約自他兩明，以臨說戒，必須行淨故。事非中。一人獨秉，眾具須備。時非者越三日故。

The third. Under 'invalidity of persons': it also clarifies both self and others, because when approaching the recitation of precepts, one's conduct must be pure. Under 'invalidity of matter': one person conducting it alone must have all requisites complete. 'Invalidity of time' is because of exceeding three days.