釋氏要覽 1.219

1.219

律云。時跋難陀在眾。儀貌昂藏。舍利弗形容短小。有外道欲出家。竊作是念。此小比丘智慧尚爾。況堂堂者乎乃投跋難陀出家受戒後問師經律論。悉不能通。外道却言佛法淺近。嫌諸比丘。反歸本道。

The Vinaya says: At that time Upananda was in the assembly, with an imposing and dignified demeanor, while Śāriputra had a short and small physique. A non-Buddhist who wished to leave the household life secretly thought: 'If this small bhikṣu's wisdom is already like this, how much more so that majestic one!' He then turned to Upananda to leave the household life and receive the precepts. Later, when he questioned his teacher on the sūtras, vinaya, and śāstras, the teacher could understand none of them. The non-Buddhist then said that the Buddhadharma was shallow and superficial, resented the bhikṣus, and returned to his original path.