Shatapatha Brahmana 1.9.2.21

1.9.2.21

atha vedam patnī visraṃsayati | yoṣā vai vedirvṛṣā vedo mithunāya vai ved!aḥ kriyate 'tha yadenena yajña upālabhate mithunamevaitatprajananaṃ kriyate

The mistress then unties the veda-bunch. The altar (vedi) assuredly is female and the veda is male. For union the veda was made: and accordingly when he touches, (the altar) with it during the sacrifice, a union productive of offspring is thereby effected.