Naradapurana 1.24.18

Nāradapurāṇa 1.24.18

brāhmaṇakṣatriyaviśāṃ śūdrāṇāṃ ca dvijottamā /
kriyāḥ sāmānyato vakṣye tacchṛṇuṣva samāhitaḥ //