Bhashya
तत्रैकविंशत्यक्षरसरूपया आदित्यमाप्नोति मृत्युम् ।यस्मादेकविंश इत अस्माल्लोकात् असावादित्य सङ्ख्यया ।'द्वादश मासा पञ्चर्तवस्त्रय इमे लोका असावादित्य एकविंश' इति श्रुते, अतिशिष्टेन द्वाविंशेनाक्षरेण पर मृत्यो आदित्यात् जयति आप्नोतीत्यथ ।यच्च तदादित्यात्परम्, किं तत् ? नाकम्, कमिति सुख तस्य प्रतिषेधोऽक तन्न भवतीति नाकम्, कमेवेत्यर्थ, अमृत्युविषयत्वात् ।विशोक च तत् विगतशोक मानसदुःखरहितमित्यर्थ — तदाप्नोतीति ॥
In plain words
Through the twenty-one-syllable measure one masters the sun, which is death—for the sun stands as the twenty-first, counting the twelve months, five seasons, and three worlds, as the scripture declares. Then, with the surplus twenty-second syllable, one transcends death and the sun itself. And what lies beyond the sun? It is Nāka, the sorrowless realm free from mental pain, where supreme bliss abides beyond the reach of death. That is what one attains.
Close to the Sanskrit
There, with the twenty-one-syllable form he attains the sun, death. Because from here, this world, that sun is twenty-first by counting: 'Twelve months, five seasons, these three worlds, that sun is the twenty-first', thus the Sruti says. With the remaining twenty-second syllable he conquers and attains higher than death, than the sun. And what is that beyond the sun? What is it? Nāka—'ka' is happiness, its negation is 'aka', meaning that in which 'ka' is not, is nāka, or rather happiness indeed, because it is beyond the realm of death. And that is sorrowless, completely free from mental grief—that he attains.