Muṇḍaka Upaniṣad · 3.1.1

द्वा सुपर्णा सयुजा सखाया समानं वृक्षं परिषस्वजाते । तयोरन्यः पिप्पलं स्वाद्वत्त्यनश्नन्नन्यो अभिचाकशीति

dvā suparṇā sayujā sakhāyā samānaṃ vṛkṣaṃ pariṣasvajāte | tayor anyaḥ pippalaṃ svādv atty anaśnann anyo abhicākaśīti

Two birds of beautiful wings, companions united, cling to the same tree. One of them eats the sweet fruit; the other, not eating, simply observes.

This verse, also found in the Ṛg-Veda and the Śvetāśvatara Upaniṣad, is one of the most profound metaphors in Indian philosophy: the two birds in the tree.

Dvā suparṇā — two birds of beautiful wings (su-parṇa). They are identical in appearance, both beautiful, both with wings. They represent two aspects of ourselves.

Sayujā sakhāyā — united, companions. Sayuja indicates intimate union; sakhāya, friendship. They are not strangers but inseparable companions from all eternity.

Samānaṃ vṛkṣam — the same tree. The tree is the body, or more broadly, the field of experience (kṣetra). It is also interpreted as the tree of saṃsāra, with its roots upward (in the transcendent) and its branches downward (in manifestation).

Pippalaṃ svādv atty — eats the sweet fruit of the pippala. One bird is busy tasting the fruits: pleasures and pains, sweet and bitter experiences. This is the jīva, the individual soul caught in identification with the body-mind.

Anaśnann anyo abhicākaśīti — the other, not eating, simply observes. The second bird does not touch the fruits. It does not act, does not experience karma. It only witnesses (sākṣī). This is the Ātman, pure consciousness, ever free.

The teaching: both birds are us. When we identify with experience, we suffer. When we recognize our nature as the witness, we discover we have never eaten any fruit, we have never suffered. Suffering belongs to the first bird; freedom is the nature of the second.