Yāska's Nirukta 2.20

2.20

``ruśadvatsā ruśatī śvetyā āgād āraik u kṛsnā sadanāny asyāh/
samāna bandhū amṛte anūcī dyāvā varṇaṃś carata āmināne/''
ruśat vatsā sūrya vatsā,.ruśad iti varṇa nāma,.rocater jvalati karmaṇah/
sūryam asyā vatsam āha,.sāhacaryād rasa haranād vā/
``ruśatī śvetyāgāt/''.śvetyā śvetater aricat kṛsnā sadanāy asyāḥ kṛsna varṇā rātrih/
kṛsnam kṛsyater nikṛṣṭo varṇah/
atha ene saṃstauti samāna bandhū samāna bandhana1d amṛta1d amarana dharmānāv,.anūcī anūcyāv iti itaretaram abhipretya,.''.dyāvā varṇaṃś caratas''.te eva dyāvau,.dyotanād/
api vā dyāvā caratas tayā saha caratas iti syād/
āmināne āminvāne anyonyasya adhyātmam kurvāne/
ahar nāmāny uttarāni dvādaśa/
ahar kasmād upāharanty asmin karmāṇi/
tasya eṣa nipātas bhavati vaiśvānarīyāyām ṛci/