The works of Ādi Śaṅkarācārya

Bṛhadāraṇyakopaniṣadbhāṣyam

Verse 153

यः प्राणे तिष्ठन्प्राणादन्तरो यं प्राणोन वेद यस्य प्राणः शरीरं यः प्राणमन्तरोयमयत्येष त आत्मान्तर्याम्यमृतः ॥ १६ ॥

In plain words

The one who lives inside your very breath, yet is nothing the breath can claim as its own, whom the breath itself never knows, whose body the breath is, who governs it from within -- that is your self, the ruler seated inside everything, and death does not touch him.

Close to the Sanskrit

He who, dwelling in the breath, is other than the breath, whom the breath does not know, whose body the breath is, who controls the breath from within -- he is your self, the inner controller, immortal.