CHĀNDOGYA UPANISHAD · 1.11.5

प्राण इति होवाच ।
सर्वाणि ह वा इमानि भूतानि प्राणम् एवाभिसंविशन्ति ।
प्राणम् अभ्युज्जिहते ।
सैषा देवता प्रस्तावम् अन्वायत्ता ।
तां चेद् अविद्वान् प्रास्तोष्यो मूर्धा ते विपतिष्यत् तथोक्तस्य मयेति ॥

prāṇa iti hovāca ।
sarvāṇi ha vā imāni bhūtāni prāṇam evābhisaṃviśanti ।
prāṇam abhyujjihate ।
saiṣā devatā prastāvam anvāyattā ।
tāṃ ced avidvān prāstoṣyo mūrdhā te vipatiṣyat tathoktasya mayeti ॥

He said: 'Breath (prâna). For all these beings merge into breath alone, and from breath they arise. This is the deity belonging to the prastâva. If, without knowing that deity, you had sung forth your hymns, your head would have fallen off, after you had been warned by me.'

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