यो रेतसि तिष्ठन्रेतसोऽन्तरो यँ रे-तो न वेद यस्य रेतः शरीरं यो रेतोऽन्त-रो यमयत्येष त आत्मान्तर्याम्यमृतोऽदृ-ष्टो द्रष्टाश्रुतः श्रोतामतो मन्ताविज्ञातोविज्ञाता नान्योऽतोऽस्ति द्रष्टा नान्योऽ-तोऽस्ति श्रोता नान्योऽतोऽस्ति मन्तानान्योऽतोऽस्ति विज्ञातैष त आत्मान्त-र्याम्यमृतोऽतोऽन्यदार्तं ततो होद्दालकआरुणिरुपरराम ॥ २३ ॥
In plain words
The one who lives inside the very seed of life, yet is nothing the seed can claim as its own, whom the seed itself never knows, whose body the seed is, who governs it from within -- that is your self, the ruler seated inside everything, and death does not touch him. He sees without ever being seen, hears without ever being heard, thinks without ever being thought, understands without ever being understood. There is no other seer anywhere but him. No other hearer. No other thinker. No other one who understands. This -- only this -- is your self, ruling from within, beyond death. Everything else wears down and suffers. At that, Uddalaka, son of Aruna, fell silent.
Close to the Sanskrit
He who, dwelling in the seed, is other than the seed, whom the seed does not know, whose body the seed is, who controls the seed from within -- he is your self, the inner controller, immortal: the unseen seer, the unheard hearer, the unthought thinker, the ununderstood understander. There is no other seer than this; there is no other hearer than this; there is no other thinker than this; there is no other understander than this. This is your self, the inner controller, immortal. Other than this, everything is subject to affliction. Thereupon Uddalaka, son of Aruna, fell silent.