《资治通鉴·唐纪·唐纪三十》
再说古代的将军受命出征，都要凿一面向北的门，从那里出去，以示战死的决心。而盖嘉运现在却朝夕饮酒作乐，没有忧国忧民之心。
且将军受命，凿凶门而出；今乃酣宴朝夕，殆非忧国爱人之心。
In ancient times, before generals set off on an expedition, they would open a door facing north to show their determination to fight to the death. But at present, Gai Jiayun is only immersed in wine and entertainment without any concerns for the state and people.