《管子·君臣上》
上面对君主言无不尽，下面为人民出力办事，而能够奉公守法服从命令的，那就是忠臣。
能上尽言于主，下致力于民，而足以修义从令者，忠臣也。
A loyal minister is the one who does his duty for the people and obeys the orders, speaking out to the monarch and serving the people.