Kaṭha Upaniṣad · 2.3.1

ऊर्ध्वमूलोऽवाक्शाख एषोऽश्वत्थः सनातनः । तदेव शुक्रं तद्ब्रह्म तदेवामृतमुच्यते । तस्मिंल्लोकाः श्रिताः सर्वे तदु नात्येति कश्चन

ūrdhvamūlo'vākśākha eṣo'śvatthaḥ sanātanaḥ | tadeva śukraṃ tadbrahma tadevāmṛtamucyate | tasmiṃllokāḥ śritāḥ sarve tadu nātyeti kaścana

With roots above and branches below, this Aśvattha tree is eternal. That is the pure, that is Brahman, that is called the immortal. In it rest all the worlds; no one transcends it.

The image of the inverted tree is one of the most powerful in Upanishadic literature, famously taken up in the Bhagavad Gītā (chapter 15).

Ūrdhva-mūla — with roots above. The tree of the world has its root on high, in Brahman, the supreme reality. Roots are the origin; placing them above inverts the ordinary perspective: the supreme is not below (on earth) but above (in transcendence).

Avāk-śākha — with branches downward. The branches of this tree extend downward, toward manifestation. They are the worlds, the beings, the experiences — all that we know as “creation.”

Aśvattha — the sacred fig tree (Ficus religiosa), the bodhi tree under which the Buddha attained enlightenment. Etymologically it can be interpreted as “a-śva-ttha” — that which will not remain until tomorrow, the impermanent. Paradoxically, this impermanent tree is sanātana — eternal. Manifestation changes continuously but the process itself is without beginning or end.

Tad eva śukram — That is the pure, the luminous. Tad brahma — That is Brahman. Tad eva amṛtam — That is the immortal. Triple identification pointing to the root of the tree: Brahman.

Tasmin lokāḥ śritāḥ sarve — in Him rest all the worlds. Everything manifested depends on Brahman for its existence. Tadu nātyeti kaścana — no one goes beyond Him. Brahman is the absolute limit; there is no reality beyond.

For the yogi, contemplating this inverted tree is to remember that the source of all is “above” — not in the spatial sense but in the sense of the subtlest, the most interior, the most essential.