BṚHADĀRAṆYAKA UPANISHAD · 3.7.4

यो ऽप्सु तिष्ठन्न् अद्भ्यो ऽन्तरो यम् आपो न विदुर् यस्यापः शरीरं यो ऽपो ऽन्तरो यमयत्य् एष त आत्मान्तर्याम्य् अमृतः ॥

yo ’psu tiṣṭhann adbhyo ’ntaro yam āpo na vidur yasyāpaḥ śarīraṃ yo ’po ’ntaro yamayaty eṣa ta ātmāntaryāmy amṛtaḥ ॥

'He who dwells in the water, and within the water, whom the water does not know, whose body the water is, and who pulls (rules) the water within, he is thy Self, the puller (ruler) within, the immortal.'