《左传·成公·成公六年》
卫国因为相信晋国，所以军队驻扎在他们郊外而不加防守，如果袭击他们，这是丢弃信用。
卫唯信晋，故师在其郊而不设备。若袭之，是弃信也。
Wei trusted Jin and did not put on their guard in the suburbs when Jin's army stationed there. It is not loyal to attack them now.