Shvetashvatara Upanishad Verse 1.14

Sanskrit

स्वदेहमरणिं कृत्वा प्रणवं चोत्तरारणिम् ।
ध्याननिर्मथनाभ्यासाद् देवं पश्येन्निगूढवत् ॥ १४॥

Transliteration

svadeham araṇiṃ kṛtvā praṇavaṃ cottarāraṇim |
dhyānanirmathanābhyāsād devaṃ paśyen nigūḍhavat || 14 ||

Translation

By making one’s own body the lower friction-stick and the Pranava (Om) the upper friction-stick, and by practicing the friction of meditation, one should see the hidden God, as it were.