Yāska's Nirukta 317.1.6

317.1.6

"katamat tadetadakṣaram" ? "oṃ"--"ityeṣā vāk"--"iti śākapūṇeḥ" abhiprāyaḥ | oṃkāramṛte na hyarthayanti | tasyāḥ "akṣare" "parame" "vyoman" vyomavividhamasmin śabdajātamotarbhitaṃ vyoma tasmin, tisṛṣu mātrāsu akārokāramakāralakṣaṇāsūpaśāntāsu yadavaśiṣyate, tadakṣaraṃ paramaṃ vyoma, aparamākāśam apekṣya tatparaṃ vyoma, śabdasāmānyamabhivyaktamityabhiprāyaḥ | "yasmin devā adhiniṣaṇṇāḥ sarve" | ṛgādiṣu ye devāḥ, te mantradvāreṇā'kṣare niṣaṇṇāḥ, tasya śabdakāraṇatvāt | tedyathā, prathamāyāṃ mātrāyāṃ pṛthivī, agniḥ, ṛgvedaḥ, pṛthivīlokanivāsina ityeva, dvitīyāyāṃ mātrāyāma antarikṣam, vāyuḥ, yajūṃṣi, tallokanivāsino janā iti, tṛtīyāyāṃ mātrāyāṃ dyauḥ, ādityaḥ, sāmāni, tallokanivāsinī janā iti | vijñāyate hi--"oṃkāra evedaṃ sarvam"--iti | "yastanna veda" anayā vibhūtyākṣaram, "kim" asau "ṛcā" ṛgādibhirmantraiḥ "kariṣyati" ? yastainākṣarātmanā paśyati | "ya ittadvidusta ime samāsate--iti viduṣa upadiśati" | te hi tatparajñānātsāmrājyamupagatāḥ praṇavavigrahamātmānamanupraviśya samīkṛtā nirvāānti śāntārciṣa ivānalā iti | 13 | 10 |