Mahabharata 12.57.15
चातुर्वर्ण्यस्य धर्माश्च रक्षितव्या महीक्षिताधर्मसंकररक्षा हि राज्ञां धर्मः सनातनः
cāturvarṇyasya dharmāśca rakṣitavyā mahīkṣitādharmasaṃkararakṣā hi rājñāṃ dharmaḥ sanātanaḥ
Our plain-language meaning of this verse is waiting for scholar review.
Open in the book