阿彌陀經通贊疏 1.70

1.70

贊曰：第五多聞密行對。梵云阿難陀，此云慶喜，但言阿難，翻為歡喜亦訛也。世尊成道內外咸慶，當喜時生故云歡喜，已成聖果。又論云：尊者往昔曾為大富長者，因施誦經沙彌飲，遂發願言：「願小師成佛，願我為多聞弟子，所說教法悉能記持。」今符往願博學多聞。此尊者貌瑩秋蟾心明皎日，巖間結集誦三藏之教微言，水上分身應四王之請命，故云多聞也。

The commentary says: The fifth is the pair of great learning and esoteric practice. In Sanskrit he is called Ānanda, which is translated as "Rejoicing." Calling him simply "Anan" and translating it as "joy" is also corrupt. When the World-Honoured One attained enlightenment, all within and without rejoiced; because he was born at that joyful time, he was named "Joy"; he has already attained the holy fruit. Moreover, a treatise says: In the past, the venerable one was once a wealthy elder. Because he offered a drink to a novice reciting sūtras, he made a vow, saying: "May this little master attain buddhahood, and may I become his disciple of great learning, able to memorize and uphold all the teachings he preaches." Now, corresponding to his past vow, he is widely learned and has heard much. For this venerable one, whose appearance is pure as the autumn moon and whose mind is bright as the radiant sun, he compiled the subtle words of the Tripiṭaka teachings within the crags, and emanated manifestations upon the waters to answer the summons of the Four Heavenly Kings; hence it is called "great learning."