Vajrasuci (Siddhacarya Ghoshapada) 5

5

(ṅa) ato bhārataprāmāṇyād vyādhamṛgahaṃsacakravākadarśanasambhavānmanyāmahe12 jīvastāvad brāhmaṇo na bhavati| mānavadharmaprāmāṇyādapi
uktaṃ hi mānave dharme13adhītya caturo vedānsāṅgopāṅgena tattvataḥ
śūdrātpratigrahāhī brāhmaṇo jāyate kharaḥ

(e) Therefore, from the authority of the Mahābhārata, because the condition of hunters, deer, swans, and cakravāka birds is seen [to occur], we consider that first, the soul is not the brāhmaṇa. And also from the authority of the Laws of Manu.
For it is stated in the Laws of Manu:
Having studied the four Vedas in truth, along with the limbs and secondary limbs,
a brāhmaṇa who accepts gifts from a śūdra is born a donkey;