Mundaka-3-2-6-vedāntavijñāna

Sri Shankara’s Commentary (Bhashya) translated by S. Sitarama Sastri

Having without doubt determined the object of the knowledge of Vedanta, i.e., that Brahman should be known, the seekers, their minds purified by dint of renunciation of all karma and by being centred in the pure Brahman, attain the worlds of the Brahman at the end of samsara, which for the seekers after emancipation corresponds to the time of death of those rotating in samsara. As men who seek emancipation are many, the world of Brahman, though one, appears to be many or is reached as many; so, the plural number ‘worlds of the Brahman’ is used. Brahman being the world reached, the expression ‘in the worlds of the Brahman’ means ‘in Brahman.’ Paramritah, they whose atman has become the highest immortal, i.e., Brahman. They become the highest and immortal Brahman, even during life and are absolved in all sides like a lamp that has gone out and like the akas in the pot, i.e., they have no need of any other place to go to; for, the Sruti and the Smriti say “as the footmark of birds in the air and that of aquatic animals in water are not seen, so the track of the knowing men” and they go by no road, who would reach the ends of the roads of samsara. Motion limited by place is only in samsara, because it is accomplished by means limited; but as the Brahman is all, it cannot be reached in a limited space; if the Brahman were limited in respect of place, it would like a substance having form, have a beginning and an end, be dependent on another, composed of parts, non-eternal and be a product. But the Brahman cannot be like that; so, its attainment too, cannot be limited by conditions of place.

Links
Various resources on the Mundakopanishad
Upanishad Series – Mundakopanishad Commentary by Swami Chinmayananda