《旧唐书·本纪·卷一》
六月五日，命令太宗率兵巡行西河并下达起义的命令，攻下了西河。
六月甲申，命太宗将兵徇西河，下之。
On June 5th, they ordered Crown Prince to lead soldiers to patrol Xihe and issued the order to start the rebellion, attacking and conquering Xihe.