The cardinal virtues often referred as the three da's: damyata, datta and dayadhvam. restraint or self-control, giving and compassion respectively; are the foundation of hindu ethical thought and reflection.
According to the Brihadaranyaka Upanisad,
"The threefold offspring of Prajapati - gods, men, and demons - dwelt with their father Prajapati as students of sacred knowledge (brahmacarya).
Having lived the life of a student of sacred knowledge, the gods said: "Speak to us, sir." To them then he spoke this syllable, "Da" 'Did you understand?' 'We understand,' said they. 'You said to us, "Restrain yourselves (damyata)," 'Yes (OM)!' said he. 'You understand.'
So then the men said to him: 'Speak to us, sir.' To them then he spoke this syllable, 'Da.' 'Did you understand?' 'We did understand,' said they. 'You said to us, "Give (datta)." "Yes (OM)!" said he. 'You did understand.'
So then the demons said to him: 'Speak to us, sir.' To them, he spoke this syllable, "Da." 'Did you understand?' 'We did understand, 'said they. 'You said to us, "Be compassionate (dayadhvam). "Yes (OM)!" said he. 'You did understand.'
This same thing does the divine voice here, thunder, repeat: Da! Da! Da! that is self restraint yourselves, give, be compassionate."
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