Śatapatha Brāhmaṇa ("of a hundred paths") 3.7.2.4

3.7.2.4

tadu tathā na kuryāt | agniṣṭhamevocrayedidaṃ vai yūpamucrityādhvaryurā parivyayaṇānnānvarjatyaparivītā vā eta etāṃ rātriṃ vasanti sā nveva paricakṣā paśave vai yūpamucrayanti prātarvai paśūnālabhante tasmādu prātarevocrayet

Let him, however, not do this; but let him only set up the one opposite the fire. For after setting it up the Adhvaryu does not quit his hold of it till the girding; but those (others) remain ungirt during that night. Thus there would be an offence, since it is for the victim that the stake is set up, and the victim is (only) slaughtered on the next morning: let him therefore set up (the others) on the next morning.