法華義疏 7.56

7.56

未見經說。意謂十弟子中四大聲聞即為四人。又三藏法師云：「迦旃延解修多羅藏，優波離解毘尼藏，富留那解阿毘曇藏，阿難總持三藏，合八大人也。」

I have not seen the sūtra explain this. In my view, the four great śrāvakas among the ten disciples constitute four persons. Furthermore, the Tripiṭaka Master said: 'Kātyāyana understood the Sūtra Piṭaka, Upāli understood the Vinaya Piṭaka, Pūrṇa understood the Abhidharma Piṭaka, and Ānanda held the three piṭakas altogether; combined, they make eight great persons.'