Mahabharata 13.107.147

आगमानां हि सर्वेषामाचारः श्रेष्ठ उच्यतेआचारप्रभवो धर्मो धर्मादायुर्विवर्धते

āgamānāṃ hi sarveṣāmācāraḥ śreṣṭha ucyateācāraprabhavo dharmo dharmādāyurvivardhate

Our plain-language meaning of this verse is waiting for scholar review.