Shatapatha Brahmana 8.7.4.3

8.7.4.3

te cetayamānāḥ | etāni sāmānyapaśyaṃstānyagāyaṃstaireṣu lokeṣu rasamupajīvanamadadhustathaivaitadyajamāno yadetāni sāmāni gāyatyeṣvevaitallokeṣu rasamupajīvanaṃ dadhāti

Whilst meditating, they saw these sâmans (hymn-tunes), and sang them; and by means of them they laid sap, the means of subsistence, into these worlds; and in like manner does the Sacrificer now, when he sings these sâmans, lay sap, the means of subsistence, into these worlds.