觀無量壽佛經疏 2.21

2.21

答曰：「德高曰尊，耆年曰宿。一切凡聖知彼內德過人，識其外相殊異，故名眾所知識。」

Answer: "Exalted virtue is called venerable (zun); advanced age is called elder (su). All ordinary and noble beings knew their inner virtues surpassed others, and recognized their outer appearance as extraordinarily distinguished; hence they are called 'known and recognized by the assembly'."