Shatapatha Brahmana 1.9.2.22

1.9.2.22

atha yatpatnī visraṃsayati | yoṣā vai patnī vṛṣā vedo mithunamevaitatprajananaṃ kriyate tasmādvedaṃ patnī visraṃsayati

And (the reason) why it is the mistress who unties the veda (is this): the mistress is female and the veda is male; consequently a union productive of offspring is thereby effected: this is why the mistress unties the veda.