成唯識論演祕 1.138

1.138

受等不行名為受斷樂，即滅定。受斷之樂，依主立名，體即滅定。

When feeling and so on do not function, it is called the pleasure of the cessation of feeling; that is, the attainment of cessation (nirodha-samāpatti). The pleasure of the cessation of feeling takes its name from the determinative compound (tatpuruṣa); its essence is just the attainment of cessation.