大般涅槃經義記 5.299

5.299

上來類答，自下總答，亦名通答。於中有四：一體性不同，故立四種。文中直言「是無量心體性有四」，略不具論，何者是乎？愛憐之心是慈之性、惻愴之懷是悲之性、慶悅之意是喜之性、忘懷之慮是捨之性。心無存著，故曰忘懷。

The preceding was the analogical reply; from here below is the general reply, also called the comprehensive reply. Within this there are four points: First, because their essential natures are different, four kinds are established. In the text it simply says, "The essential natures of these immeasurable minds are four," omitting a full discussion; what are they? A mind of affection and compassion is the nature of benevolence (maitrī); a feeling of sorrow and commiseration is the nature of compassion (karuṇā); a sentiment of joy and delight is the nature of sympathetic joy (muditā); a thought that forgets personal attachment is the nature of equanimity (upekṣā). Because the mind holds no clinging, it is said to "forget personal attachment."