Bhashya
न वै तत्र यतोऽह ब्रह्मलोकादागत तस्मिन्न वै तत्र एतदस्तियत्पृच्छसि ।न हि तत्र निम्लोच अस्तमगमत्सविता न चउदियाय उद्गत कुतश्चित् कदाचन कस्मिंश्चिदपि काले इति ।उदयास्तमयवर्जित ब्रह्मलोक इत्यनुपपन्नम् इत्युक्त शपथ मिव प्रतिपेदे—हे देवा साक्षिणो यूय शृणुत, यथा मयाक्त सत्य वच्च तेन सत्येन अह ब्रह्मणा ब्रह्मस्वरूपेण मा विराधिषि मा विरुध्येयम्, अप्राप्तिर्ब्रह्मणो मम मा भूदित्यर्थ ॥
In plain words
Not indeed is that which you ask present in the realm from which I have come; for there the sun neither sets nor rises from anywhere at any time. When told that it is illogical for the world of Brahman to be free of sunrise and sunset, he took on the tone of one swearing an oath: Listen, O gods, my witnesses—by the truth of what I have spoken, may I not be separated from Brahman, the very reality of my own self, and may I never miss attaining the ultimate truth.
Close to the Sanskrit
Not indeed there from where I have come from the world of Brahman, in that indeed there this exists which you ask. For not there sunset went the sun nor rose up, from anywhere, ever, in any time whatsoever, thus. That a world free from rising and setting is the world of Brahman is inconsistent, thus being addressed, as if an oath he undertook—O gods, witnesses, you listen, as my spoken word is true, by that truth may I not fail in Brahman by the nature of Brahman, may I not oppose, may non-attainment of Brahman not be for me, this is the meaning.