大乘義章 11.66

11.66

功能別者，慈能與樂，悲能拔苦，喜能慶物，捨能齊益怨親等故（此二門竟）。

As for the difference in function: loving-kindness can bestow bliss, compassion can eradicate suffering, sympathetic joy can celebrate beings, and equanimity can equally benefit enemies and kin alike, and so forth (this completes the second section).