Two sweet friends .
There are two birds, two sweet friends, who dwell on the self-same tree. The one eats the fruits thereof, and the other looks on in silence.
That’s it. Do you see the image ? With your mind’s eye. Two birds in a tree. On a warm day. One is eating a fruit. The other is just looking on. On a warm day. In a tree. Two birds. Gentle wind.
Then the author continues. Hold your image. Or maybe forget the following. Do not think of the purple elephant.
The first is the human soul who, resting on that tree, though active, feels sad in his unwisdom. But on beholding the power and the glory of the higher Spirit, he becomes free from sorrow.
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 From the Svetasvatara Upanishad, part 4, in the Penguin Classics edition ‘The Upanishads’, 1965, translation by Juan Mascaró (de Mallorca).
The exact same copla also occurs as the very first lines of the Mundaka Upanishad.
See also this nice article for an interpretation of the text.
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