瑜伽論記 11.54

11.54

此就眾生緣中釋名，若然法緣無緣慈悲喜捨云何得名，法緣無量是人空智，無緣無量是其證智，二智起時實無哀怜惻愴等四行差別，由此智故能起有情緣中慈悲喜捨別相行解，從果受稱，是故亦立四種之名。

This explains the names in the context of being conditioned by sentient beings. If so, how do loving-kindness, compassion, sympathetic joy, and equanimity that are conditioned by dharmas and unconditioned receive their names? The immeasurable conditioned by dharmas is the wisdom of the emptiness of persons; the unconditioned immeasurable is the realizing wisdom. When these two wisdoms arise, they genuinely lack the distinctions of the four modes of activity such as pity and sorrowful sympathy; however, because of this wisdom, one can give rise to the distinct mental activities and understandings of loving-kindness, compassion, sympathetic joy, and equanimity conditioned by sentient beings. They receive their designations from the effect, and therefore the four names are established.