CHĀNDOGYA UPANISHAD · 3.14.1

सर्वं खल्व् इदं ब्रह्म तज्जलान् इति शान्त उपासीत ।
अथ खलु क्रतुमयः पुरुषो यथाक्रतुर् अस्मिंल् लोके पुरुषो भवति तथेतः प्रेत्य भवति ।
स क्रतुं कुर्वीत ॥

sarvaṃ khalv idaṃ brahma tajjalān iti śānta upāsīta ।
atha khalu kratumayaḥ puruṣo yathākratur asmiṃl loke puruṣo bhavati tathetaḥ pretya bhavati ।
sa kratuṃ kurvīta ॥

All this is Brahman (n.) Let a man meditate on that (visible world) as beginning, ending, and breathing in it (the Brahman). Now man is a creature of will. According to what his will is in this world, so will he be when he has departed this life. Let him therefore have this will and belief:

F. Max Müller · The Upanishads, Sacred Books of the East 1 (1879)