From The BrhadaranyakaUpanisad 5.2.1
Three classes of Prajapati’s sons – the gods, human beings and demons (devas, manushyas and asuras) – lived a life of austerity as students with their father, the Creator.
All of them, on the completion of their term, said, "Please instruct us."
Prajapati uttered before them the syllable ‘da’ and asked, "Have you understood?"
The gods thought: “We are the inhabitants of happy regions in the heavens. We gain those regions as our rewards for leading meritorious and virtuous lives. For us the pursuit of pleasure becomes the business of life. Unless we avail ourselves of the superior opportunity available there to attain the knowledge of Brahman (Supreme Self), we would have dissipated all our acquired merits and virtues in the indulgence of the senses, and we would have to start again at the human level. For us gods, pleasures of the flesh (senses) is the temptation and the control of the senses is our ally.”
The gods said to Prajapati: "Yes we have understood. You have asked us to CONTROL OURSELVES." [da = daamyata]
Prajapati was happy; he said, "Yes, you have understood."
The human beings talked it over between themselves and reflected: We men are generally avaricious and selfish. Therefore Prajapati has told us to have a charitable heart. Therefore what he means is that we should give freely, and with love, our ability, time, wealth, service and all that we ourselves value.”
The humans said, "Yes, we have understood. You have asked us to GIVE." [da = data]
Prajapati said, "Yes, you have understood."
The demons also discussed the instruction received with all sincerity. They pondered, “We have been cruel. We have seldom acted without being harsh. We have inflicted pain on everybody. Our father expects us to learn kindness.”
The demons said, “Yes, we have understood. You have asked us to be compassionate.” [da = dayadhvam]
Prajapati said, “Yes. You have understood.”
No wonder we hear this message from thunder in the sky, “da, da, da”!
ILLUSTRATIONS BY DEBA.