Shatapatha Brahmana 9.1.2.34

9.1.2.34

te cetayamānāḥ | etāni sāmānyapaśyaṃstairenam paryagāyaṃstairetamātmānamanasthikamamṛtamakurvata tathaivaitadyajamāno yadenaṃ sāmabhiḥ parigāyatyetamevaitadātmānamanasthikamamṛtaṃ kurute sarvataḥ parigāyati sarvata evaitadetamātmānamanasthikamamṛtaṃ kurute tiṣṭhangāyati tiṣṭhantīva vā ime lokā atho tiṣṭhanvai vīryavattaro hiṅkṛtya gāyati tatra hi sarvaṃ kṛtsnaṃ sāma bhavati

Whilst meditating, they saw those sâman-hymns, and sang them round about it, and by means of them they made that body of theirs boneless and immortal; and in like manner does the Sacrificer, when he sings the sâman-hymns round about it, make that body of his boneless and immortal. On every side he sings: everywhere he thus makes that body of his boneless and immortal. Standing he sings, for these worlds stand, as it were; and whilst standing one doubtless is stronger. He sings, after uttering (the syllable) 'him,' for therein the sâman-hymn becomes whole and complete.