Mahabharata 13.131.45

एतैः कर्मफलैर्देवि न्यूनजातिकुलोद्भवःशूद्रोऽप्यागमसंपन्नो द्विजो भवति संस्कृतः

etaiḥ karmaphalairdevi nyūnajātikulodbhavaḥśūdro'pyāgamasaṃpanno dvijo bhavati saṃskṛtaḥ

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