八識規矩補註 1.34

1.34

言此第六識於三性、三界并五受，恒常轉變改易也。以行相易脫故，唯受有五種。論說不一，謂七、八二識唯是捨受，前五轉識苦、樂二受，第六意識，二師說異：若意地有苦師言，第六通具五受；若意地無苦師言，第六唯憂、喜、捨三受。若約極苦極樂其苦樂之觸，豈有不侵心者哉？若無間之苦、三禪之樂，孰能忘其逆順之境？蓋逼悅於身名苦樂受，逼悅心者名憂喜受，不逼不悅者名捨受，以理言之，意地有苦師，盡其義也。

This means that this sixth consciousness constantly transforms and changes among the three natures, the three realms, and the five feelings, because its cognitive form easily shifts. Only regarding the feelings are there five kinds, and the treatises do not agree: it is said that the seventh and eighth consciousnesses have only equanimity feeling, the first five evolving consciousnesses have painful and pleasant feelings, while regarding the sixth manovijñāna, two masters differ in their accounts. The master who maintains that there is pain in the mental plane says that the sixth completely possesses the five feelings; the master who maintains that there is no pain in the mental plane says that the sixth has only the three feelings of grief, joy, and equanimity. Yet when considering extreme pain and extreme pleasure, how could their contact with pain and pleasure not penetrate the mind? With the pain of Avīci or the pleasure of the third dhyāna, who could forget their distressing or agreeable objects? What oppresses or gladdens the body is called painful or pleasant feeling; what oppresses or gladdens the mind is called grief or joy feeling; and what neither oppresses nor gladdens is called equanimity feeling. Speaking according to principle, the master who maintains that there is pain in the mental plane exhausts the meaning.