Śatapatha Brāhmaṇa ("of a hundred paths") 1.3.2.11

1.3.2.11

yajamāna eva juhūmanu | yo 'smā arātīyati sa upabhṛtamanvattaiva juhūmanvādya upabhṛtamanvattaiva juhūrādya upabhṛtsa vai caturjuhvāṃ gṛhṇātyaṣṭau kṛtva upabhṛti

Now the sacrificer stands behind the guhû, and he who means evil to him stands behind the upabhrit. The eater stands behind the guhû, and what (or, he who) is to be eaten stands behind the upabhrit. And the guhû, indeed, is the eater, and the upabhrit is that which is to be eaten. In the guhû he takes four times (with the sruva), and in the upabhrit eight times.