Shatapatha Brahmana 14.1.1.31

14.1.1.31

aśūdrociṣṭī eṣa vai dharmo ya eṣa tapati saiṣā śrīḥ satyaṃ jyotiranṛtaṃ strī śūdraḥ śvā kṛṣṇaḥ śakunistāni na prekṣeta necriyaṃ ca pāpmānaṃ ca nejjyotiśca tamaśca netsatyānṛte saṃsṛjānīti

And whilst not coming into contact with Sûdras and remains of food; for this Gharma is he that shines yonder, and he is excellence, truth, and light; but woman, the Sûdra, the dog, and the black bird (the crow), are untruth: he should not look at these, lest he should mingle excellence and sin, light and darkness, truth and untruth.