CHĀNDOGYA UPANISHAD · 6.2.1

सद् एव सोम्येदम् अग्र आसीद् एकम् एवाद्वितीयम् ।
तद् धैक आहुर् असद् एवेदम् अग्र आसीद् एकम् एवाद्वितीयम् ।
तस्माद् असतः सज् जायत ॥

sad eva somyedam agra āsīd ekam evādvitīyam ।
tad dhaika āhur asad evedam agra āsīd ekam evādvitīyam ।
tasmād asataḥ saj jāyata ॥

'In the beginning,' my dear, 'there was that only which is (τὸ ὄν), one only, without a second. Others say, in the beginning there was that only which is not (τὸ μὴ ὄν), one only, without a second; and from that which is not, that which is was born.

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