Shatapatha Brahmana 5.5.4.28

5.5.4.28

taṃ śikyodutam | uparyuparyāhavanīyaṃ dhārayanti sā yā pariśiṣṭā parisrudbhavati tāmāsiñcati tāṃ vikṣarantīmupatiṣṭhate pitṝṇāṃ somavatāṃ tisṛbhirṛgbhiḥ pitṝṇām barhiṣadāṃ tisṛbhirṛgbhiḥ pitṝṇāmagniṣvāttānāṃ tisṛbhirṛgbhistadyadevamupatiṣṭhate yatra vai soma indramatyapavata sa yatpitṝnagacattrayā vai pitarastenaivainametatsamardhayati kṛtsnaṃ karoti tasmādevamupatiṣṭhate

This (pitcher), hung up by a sling, they hold just over the Âhavanîya. He pours into it what spirituous liquor has been left over, and whilst it is trickling through, he stands by worshipping with the three verses of the Pitarah Somavantah (the Fathers accompanied by Soma), with three verses of the Pitaro Barishadah (the Fathers seated on the barhis), and with three verses of the Pitaro Agnishvâttâh (the Fathers consumed by the fire). And as to why he thus stands by worshipping,--when Soma flowed through Indra, what part of it then went to the Fathers--there being three kinds of Fathers--therewith he now supplies him and makes him whole: therefore he thus stands by worshipping.