《左传·成公·成公七年》
申、吕两地之所赖以成为城邑的，是因为从这里征发兵赋，以抵御北方。
此申、吕所以邑也，是以为赋，以御北方。
The reason that Shen and Lu are able to stand as counties is because they raise and send troops and provisions from there to defend against the north.