The Prashna Upanishad with Shankara’s Commentary
अथ यदि द्विमात्रेण मनसि संपध्यते सोऽन्तरिक्शं यजुर्भिरुन्नीयते सोमलोकम् । स सोमलोके विभुतिमनुभूय पुनरावर्तते ॥ ४ ॥
atha yadi dvimātreṇa manasi saṃpadhyate so'ntarikśaṃ yajurbhirunnīyate somalokam | sa somaloke vibhutimanubhūya punarāvartate || 4 ||
4. But if he meditates on its second mâtra only, he becomes one with mind. He is conducted into intermediate space—the world of the moon—by yajus. Having enjoyed greatness there, he returns again.
Com.—Now again, if he meditates on the syllable ‘Om,’ by its second mâtra, he becomes one with the moon, of the nature of dreams, in the form of Yajur Vêda, worthy of meditation. Thus become immortal] is taken by the yajus representing the second mâtra to the lunar world, the support of antariksha,. intermediate space, and representing the second mâtra. The meaning is that he is taken by the yajus to be born in the lunar world. Haying there, in the lunar world, enjoyed greatness returns again to the world of men.