Śatapatha Brāhmaṇa ("of a hundred paths") 7.5.2.19

7.5.2.19

atha dakṣiṇato gām | ajasramindumaruṣamiti somo vā induḥ sa haiṣa somo 'jasro yadgaurbhuraṇyumiti bhartāramityetadagnimīḍe pūrvacittiṃ namobhirityāgneyo vai gauḥ pūrvacittimitimiti prāñcaṃ hyagnimuddharanti prāñcamupacaranti sa parvabhirṛtuśaḥ kalpamāna iti yadvā eṣa cīyate tadeṣa parvabhirṛtuśaḥ kalpate gām mā hiṃsīraditiṃ virājamiti virāḍvai gaurannaṃ vai virāḍannamu gauḥ

Then on the right side (the head of) the bull, with (Vâg. S. XIII, 43), 'The imperishable, red drop,' the drop doubtless is Soma; and that bull is the same as the imperishable Soma;--'the eager one (bhuranyu),' that is, the bearer (bhartri);--'Agni, the forward-striving, I glorify with homages;' for the bull is sacred to Agni; and 'the forward-striving,' he says, because forward (towards the east) they hold up Agni, and towards the front they attend upon him;--'duly fitting thyself by limbs,' when he is built up, then he does indeed duly fit himself limb by limb;--'harm not the inexhaustible, wide-ruling cow,' the cow is indeed wide-ruling (virâg), and the wide-ruling is food, and accordingly the cow is food.