योऽन्तरिक्षे तिष्ठन्नन्तरिक्षादन्तरो यमन्तरिक्षं न वेद यस्यान्तरिक्षं शरीरं योऽन्तरिक्षमन्तरो यमयत्येष त आत्मान्तर्याम्यमृतः ॥३,७.६ ॥
In plain words
He who dwells in the middle region, yet is within the middle region, whom the middle region does not know, whose body the middle region is, who from within controls the middle region — he is thy Self, the inner controller, the immortal.