《资治通鉴·唐纪·唐纪十》
凡应当宿卫者轮流值勤，兵部根据距离远近排班，路远的轮值次数较少，路近的轮值次数较勤，均一个月一轮换。
凡当宿卫者番上，兵部以远近给番，远疏、近数，皆一月而更。
All guards are part of a rotating roster, with the frequency of their duty determined by the Ministry of War, in accordance with the distance to the imperial palace. Soldiers who live far away go on duty less often, while those who live nearby go on duty more often. All guards are scheduled for duty once a month.