Katha Upanishad Verse 2.3.1

The universe is compared to an inverted tree, the Ashvattha, whose roots are in the pure, immortal Brahman (the root up and branches down). This ancient world-tree depends entirely on its source, and nothing can transcend it. This is the eternal Truth.

Sanskrit Verse

ऊर्ध्वमूलोऽवाक्शाख एषोऽश्वत्थः सनातनः ।
तदेव शुक्रं तद्ब्रह्म तदेवामृतमुच्यते ।
तस्मिंल्लोकाः श्रिताः सर्वे तदु नात्येति कश्चन । एतद्वैतत् ॥ १ ॥

Transliteration

ūrdhvamūlo’vākśākha eṣo’śvatthaḥ sanātanaḥ |
tadeva śukraṃ tadbrahma tadevāmṛtamucyate |
tasmiṃllokāḥ śritāḥ sarve tadu nātyeti kaścana | etadvaitat || 1 ||

Translation

Root up and branches down is this ancient asvattha tree, that (its source) is pure. That is Brahman and that alone is called immortal. On that, do all worlds depend and none passes beyond that. This verily is that.