釋氏要覽 3.231

3.231

因果經云。婆羅門優陀夷。聰明多智。淨飯王勅為太子友。白太子言。朋友有三要法。一者見有失輒相曉諫。二見有好事深生隨喜。三在苦厄不相棄捨。

The Scripture of Cause and Effect says: 'The brāhmaṇa Udāyin was intelligent and very wise. King Śuddhodana ordered him to be a friend to the Crown Prince. He said to the Crown Prince: "Friends have three essential practices: first, upon seeing a mistake, immediately enlighten and admonish each other; second, upon seeing a good deed, give rise to deep sympathetic joy; third, in times of suffering and distress, do not abandon one another."'