Mahabharata 12.276.17

मार्दवं सर्वभूतेषु व्यवहारेषु चार्जवम्वाक्चैव मधुरा प्रोक्ता श्रेय एतदसंशयम्

mārdavaṃ sarvabhūteṣu vyavahāreṣu cārjavamvākcaiva madhurā proktā śreya etadasaṃśayam

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