यस्तमसि तिष्ठंस्तमसोऽन्तरो यं त-मो न वेद यस्य तमः शरीरं यस्तमोऽन्त-रो यमयत्येष त आत्मान्तर्याम्यमृतः ॥
In plain words
The one who lives inside the dark, yet is nothing the dark can claim as its own, whom darkness itself never knows, whose body darkness 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 darkness, is other than darkness, whom darkness does not know, whose body darkness is, who controls darkness from within -- he is your self, the inner controller, immortal.