Bhashya
इदानीं ब्रह्मचर्यादिसाधनानन्तरं तत्प्राप्यं च ब्रह्म प्रतिपादयितुं तृतीयचतुर्थावारभ्येते ।तत्र तावद्ब्रह्मचर्यादि साधनं श्रुत्वा तद्ब्रह्मवेदनाकाङ्क्षी प्राह धृतराष्ट्रः—
In plain words
Now that the disciplines beginning with brahmacarya have been laid out, the third and fourth chapters begin, so as to set forth brahman itself — what those disciplines are for. And here, having heard the means, Dhṛtarāṣṭra, who now wants to know that brahman, speaks:
Close to the Sanskrit
Now, immediately after the means beginning with brahmacarya, and in order to set forth brahman, which is attainable by that, the third and fourth [chapters] are begun. There, first of all, having heard the means beginning with brahmacarya, Dhṛtarāṣṭra, desirous of the knowledge of that brahman, says—