Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.1.32

2.6.1.32

sa yannātikrāmati | ita evopotthāyaṃ juhoti sakṛdu hyeva parāñcaḥ pitaro 'tha yatsakṛtsarveṣāṃ samavadyati sakṛdu hyeva parāñcaḥ pitaro 'tha yadvyatiṣaṅgamavadānānyavadyatyṛtavo vai pitara ṛtūnevaitadvyatiṣajatyṛtūntsaṃdadhāti tasmādvyatiṣaṅgamavadānānyavadyati

Now the reason why he does not walk across (to the ordinary place of offering), but pours out the oblation after stepping up (to the fire) on the sane side, is that the fathers have departed once for all; and the reason also, why he cuts but once from each of the sacrificial dishes, is that the fathers have departed once for all. And the reason why in making the cuttings, he keeps them together, is that the fathers are the seasons;--he thus keeps the seasons together, joins them to one another: that is why in making the cuttings, he keeps them together.