吞舟之鱼,不游枝流;鸿鹄高飞,不集污池。
解释:能吞下船的大鱼,不会在细浅的溪水里遨游;在天空高飞的鸿鹄,不会在肮脏的水池栖息。
Letters are the biographer's gold mine; they reveal what official records conceal.