Shatapatha Brahmana 4.5.8.4

4.5.8.4

tām prathame 'hannayet | vāgvā eṣā nidānena yatsāhasrī tasyā etatsahasraṃ vācaḥ prajātam pūrvā haiṣaiti paścādenām prajātamanvetyuttame vaināmahannayetpūrvamahāsyai prajātameti paścādeṣānveti so eṣā mīmāṃsaivottama evaināmahannayetpūrvamahāsyai prajātameti paścādeṣānveti

He may lead her up (to the sacrificial ground) on the first day; for she, the Sâhasrî, is in reality Vâk, and hers, Vâk's, is that thousandfold progeny. She walks at the head (of the other 333 cows), and behind her follows her progeny. Or he may lead her up on the last day; then her progeny precedes her, and she herself walks behind. This, however, is mere speculation: let him lead her up on the last day,--her progeny precedes her, and she herself walks behind.