Śatapatha Brāhmaṇa ("of a hundred paths") 5.4.1.2

5.4.1.2

atha yatkeśavasya puruṣasya | na vā eṣa strī na pumānyatkeśavaḥ puruṣo yadaha pumāstena na strī yadu keśavasteno na pumānnaitadayo na hiraṇyaṃ yallohāyasaṃ naite krimayo nākrimayo yaddandaśūkā atha yallohāyasam bhavati lohitā iva hi dandaśūkāstasmātkeśavasya puruṣasya

And as to why it is of a long-haired man,--such a long-haired man is neither woman nor man; for being a male, he is not a woman, and being longhaired (a eunuch), he is not a man. And copper (or bronze) is neither iron nor gold; and those mordacious ones (snakes) are neither worms nor non-worms. And as to its being copper,--reddish to be sure are mordacious ones: therefore (he throws it in the face) of a long-haired man.