यस्तमसि तिष्ठंस्तमसोऽन्तरो यं तमो न वेद यस्य तमः शरीरं यस्तमोऽन्तरो यमयत्येष त आत्मान्तर्याम्यमृतः ॥३,७.१३ ॥
In plain words
He who dwells in darkness, yet is within darkness, whom darkness does not know, whose body darkness is, who from within controls darkness — he is thy Self, the inner controller, the immortal.