Shatapatha Brahmana 4.5.8.3

4.5.8.3

sā syādapravītā | vāgvā eṣā nidānena yatsāhasryayātayāmnī vā 'yaṃ vāgayātayāmnyapravītā tasmādapravītā syāt

Let it be one that has not been approached (by a bull), for she, the Sâhasrî, is in reality Vâk (speech); but Vâk, forsooth, is of unimpaired vigour, and so is one of unimpaired vigour which has not been approached: therefore it should be one that has not been approached.