Mahabharata 3.149.36

शुश्रूषा तु द्विजातीनां शूद्राणां धर्म उच्यतेभैक्षहोमव्रतैर्हीनास्तथैव गुरुवासिनाम्

śuśrūṣā tu dvijātīnāṃ śūdrāṇāṃ dharma ucyatebhaikṣahomavratairhīnāstathaiva guruvāsinām

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