Bhashya
तद्ब्रह्म आत्मानमेव नित्यदृग्रूपमध्यारोपितानित्यदृष्ट्यादिवर्जितमेव अवेत् विदितवत् ।ननु विप्रतिषिद्धम्— 'न विज्ञातेर्विज्ञातारं विजानीयाः' इति श्रुतेः— विज्ञातुर्विज्ञानम् ।न, एवं विज्ञानान्न विप्रतिषेधः ; एवं दृष्टेर्द्रष्टेति विज्ञायत एव ; अन्यज्ञानानपेक्षत्वाच्च—न च द्रष्टुर्नित्यैव दृष्टिरित्येवं विज्ञाते द्रष्टृविषयां दृष्टिमन्यामाकाङ्क्षते ; निवर्तते हि द्रष्टृविषयदृष्ट्याकाङ्क्षा तदसंभवादेव ; न ह्यविद्यमाने विषये आकाङ्क्षा कस्यचिदुपजायते ; न च दृश्या दृष्टिर्द्रष्टारं विषयीकर्तुमुत्सहते, यतस्तामाकाङ्क्षेत ; न च स्वरूपविषयाकाङ्क्षा स्वस्यैव ; तस्मात् अज्ञानाध्यारोपणनिवृत्तिरेव आत्मानमेवावेदित्युक्तम्, नात्मनो विषयीकरणम् ॥
In plain words
That Brahman realized its own non-dual Self as pure, eternal consciousness, completely free from all transient and projected perceptions. You might object that this contradicts the scriptural warning, 'You cannot know the knower of knowledge.' We reply that there is no contradiction here. Just as the seer of vision is directly recognized, and because self-knowledge requires no auxiliary validation, once the seer's vision is understood to be eternal, all quest for an external object of perception ceases. Since an objective target does not exist, no desire to grasp it can arise. Objective sight can never turn the ultimate subject into an object of perception, nor can the Self seek its own already-attained essence. Therefore, scripture's statement that 'it knew the Self alone' simply means the eradication of superimposed ignorance, not the turning of the Self into a perceived object.
Close to the Sanskrit
That Brahman knew the Self alone, being of the nature of eternal vision and devoid of superimposed non-eternal vision etc., as one who has known. If you object that it is contradictory—from the scripture 'You should not know the knower of knowledge'—cognition of the knower. No, from such knowledge there is no contradiction; thus the seer of sight is known indeed, and because it does not depend on other knowledge—for when the seer's vision is known as eternal, one does not look for another vision regarding the seer; the desire for vision regarding the seer ceases precisely because of its impossibility, for when an object does not exist no desire arises for anyone, nor is visible sight able to make the seer an object, whence one might desire it, nor is there a desire regarding own form of oneself indeed; therefore it is said that 'knew the Self alone' is simply the cessation of the superimposition of ignorance, not the objectification of the Self.