AN 11.16
PTS: A v 342
BJT calls this the Mettanisamsa Sutta; Thai, Burmese, and PTS call it Metta Sutta.
Metta (Mettanisamsa) Sutta: Discourse on Advantages of Loving-kindness
translated from the Pali by
Piyadassi Thera
Alternate translation: Thanissaro

Thus have I heard:

On one occasion the Blessed One was living near Savatthi at Jetavana at Anathapindika's monastery. Then he addressed the monks saying, "Monks." — "Venerable Sir," said the monks, by way of reply. The Blessed One then spoke as follows:

"Monks, eleven advantages are to be expected from the release (deliverance) of heart by familiarizing oneself with thoughts of loving-kindness (metta), by the cultivation of loving-kindness, by constantly increasing these thoughts, by regarding loving-kindness as a vehicle (of expression), and also as something to be treasured, by living in conformity with these thoughts, by putting these ideas into practice, and by establishing them. What are the eleven?

1. "He sleeps in comfort. 2. He awakes in comfort. 3. He sees no evil dreams. 4. He is dear to human beings. 5. He is dear to non-human beings. 6. Devas (gods) protect him. 7. Fire, poison, and sword cannot touch him. 8. His mind can concentrate quickly. 9. His countenance is serene. 10. He dies without being confused in mind. 11. If he fails to attain arahantship (the highest sanctity) here and now, he will be reborn in the brahma-world.

"These eleven advantages, monks, are to be expected from the release of heart by familiarizing oneself with thoughts of loving-kindness, by cultivation of loving-kindness, by constantly increasing these thoughts, by regarding loving-kindness as a vehicle (of expression), and also as something to be treasured, by living in conformity with these thoughts, by putting these ideas into practice and by establishing them."

So said the Blessed One. Those monks rejoiced at the words of the Blessed One.

See also: Iti 27.