MUṆḌAKA UPANISHAD · 3.1.1

द्वा सुपर्णा सयुजा सखाया समानं वृक्षं परिषस्वजाते ।
तयोरन्यः पिप्पलं स्वाद्वत्त्यनश्नन्नन्यो अभिचाकशीति ॥ १॥

dvā suparṇā sayujā sakhāyā samānaṃ vṛkṣaṃ pariṣasvajāte ।
tayoranyaḥ pippalaṃ svādvattyanaśnannanyo abhicākaśīti ॥ 1॥

Two birds, beautiful of wing, close companions, cling to one common tree: of the two one eats the sweet fruit of the tree, the other eats not but watches his fellow.