Bhashya
तो यदुक्त तदेवेदमभिहितम् 'कस्मिन्नु भगवो विज्ञाते सर्व-मिद् विज्ञात भवति' इति , एतस्मिन्हि परस्मिन्नात्मनि सर्वकारणे पुरुषे विज्ञाते, पुरुष एवेदं विश्व नान्यदस्तीति विज्ञातभवतीति ।किं पुनरिद् विश्वमित्युच्यते-- कर्म अग्निहोत्रादिलक्षणम् , तप ज्ञान तत्कृत फलमन्यदेव तावद्धीदं सर्वम् ,तच्च एतद्ब्रह्मण कार्यम् , तस्मात्सर्व ब्रह्म परामृत परममृतमहमेवेति यो वेद निहित स्थित गुहाया हृदि सर्वप्राणिनाम् , सएव विज्ञानात् अविद्याग्रन्थि ग्रन्थमिव दृढीभूतामविद्यावा-सना बिकिरति विक्षिपति विनाशयति इह जीवन्नेव, नमृत सन् हे सोम्य प्रियदर्शन ॥
In plain words
Therefore, what was stated earlier is fully explained right here: 'O venerable sir, what is that by which, when known, all this becomes known?' When that Supreme Self, the causal Person of all, is realized, one understands that this entire universe is nothing other than the Person himself, and that no separate reality exists. And what is this universe said to be? Ritual actions like the Agnihotra, spiritual disciplines, intellectual knowledge, and the fruits produced by them—all of this belongs to the realm of effects, produced by the lower Brahman. Therefore, whoever realizes—'All is Brahman, supreme and immortal, and I myself am that supreme nectar'—recognizing Him established in the secret space within the heart of every living creature, that person shatters, scatters, and utterly destroys the deeply entrenched knot of ignorance like a physical knot. He does this right here while still alive, and not merely after death, O gentle and beloved one.
Close to the Sanskrit
Therefore what has been stated is explained right here: 'When what is known, O revered sir, all this becomes known?'—because when this supreme Self, the causal Purusha of all, is known, it is known that the Purusha alone is this universe, and nothing else exists. What again is said to be this universe? Actions characterized by Agnihotra and the like, austerity, knowledge, and the fruit produced by them—all this certainly is different, and this is the effect of Brahman. Therefore, whoever knows 'All is Brahman, supreme, immortal, the supreme nectar, and I indeed am that,' established securely in the cave in the heart of all living beings—he indeed, through realization, scatters, disperses, and destroys the deep-seated knot of ignorance like a physical knot, right here while living, not after dying, O gentle and pleasant-looking one.