Mahabharata 13.6.16

शौचेन लभते विप्रः क्षत्रियो विक्रमेण चवैश्यः पुरुषकारेण शूद्रः शुश्रूषया श्रियम्

śaucena labhate vipraḥ kṣatriyo vikrameṇa cavaiśyaḥ puruṣakāreṇa śūdraḥ śuśrūṣayā śriyam

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