Katha Upanishad - Verse 1.2.16
Text: एतद्ध्येवाक्शरं ब्रह्म एतद्ध्येवाक्शरं परम् । एतद्ध्येवाक्शरं ज्ञात्वा यो यदिच्छति तस्य तत् ॥ १६ ॥ etaddhyevākśaraṃ brahma etaddhyevākśaraṃ param | etaddhyevākśaraṃ jñātvā yo yadicchati tasya tat || 16 || 16. This word is, indeed, Brahman, this word is, in deed, the highest; whoso knows this word obtains, indeed, whatever he wishes for. Shankara’s Commentary: Therefore, the word, indeed, is Brahman, (manifested). This word, indeed, is also the highest- Brahman. For, this word is the substitute for both of them....