《淮南子·泰族训》
一国君主和他的臣民的关系，就像城墙和墙基的关系，又像树木和根基的关系，根扎得深这树木就牢固，墙基砌得好这城墙就坚实。
国主之有民也，犹城之有基，木之有根。根深则本固，基美则上宁。
The relationship between a monarch and his subjects is like that between a city wall and its foundation, or between a tree and its roots. If the roots are deep, the tree will be strong; if the foundation is well laid, the city wall will be strong.