The virtue of mudita, (Usually rendered by unselfish, sympathetic, or altruistic joy.) i.e., finding joy in the happiness and success of others.
Here, O, Monks, a disciple lets his mind pervade one quarter of the world with thoughts of unselfish joy, and so the second, and so the third, and so the fourth. And thus the whole wide world, above, below, around, everywhere and equally, he continues to pervade with a heart of unselfish joy, abundant, grown great, measureless, without hostility or ill-will.
Take a look at Practice of Metta and the English Problem, by John Aske.
Categories: Foundations of Buddhism