Brihadaranyaka-Upanishad: Fifth Adhyâya, Second Brahmana

1. The threefold descendants of Pragâpati, gods, men, and Asuras (evil spirits), dwelt as Brahmakarins (students) with their father Pragâpati. Having finished their studentship the gods said: “Tell us (something), Sir.” He told them the syllable Da. Then he said: “Did you understand?” They said: “We did understand. You told us ‘Damyata,’ Be subdued.” “Yes,” he said, “you have understood.”

2. Then the men said to him: “Tell us something, Sir.” He told them the same syllable Da. Then he said: “Did you understand?” They said: “We did understand. You told us, ‘Datta,’ Give.” “Yes,” he said, “you have understood.”

3. Then the Asuras said to him: “Tell us something, Sir.” He told them the same syllable Da. Then he said: “Did you understand?” They said: “We did understand. You told us, ‘Dayadharn,’ Be merciful.” “Yes,” he said, “you have understood.”

The divine voice of thunder repeats the same, Da Da Da, that is, Be subdued, Give, Be merciful. Therefore let that triad be taught, Subduing, Giving, and Mercy.