Jaiminīya (Talavakāra) Brāhmaṇa 58.305

58.305

gāyatrīṣu stuvanti gāyatrī vai chandasāmayātayāmnyayātayāmatāyā eva
tisṛṣu stuvanti trayo vā ime lokā -- eṣāṃ lokānāṃ samaṣṭyai
atho trayo vai prāṇāpānavyānāḥ
tānevaitatsaṃtatya teṣu pratiṣṭhāyodṛcamaśnuvate
gāyatraṃ sāma bhavatyayātayāma vai gāyatramayātayāmatāyā eva
atho mano vai gāyatram
manasaivainattatsamṛddhayanti | manasopāvartayanti | manasā hiṃkurvanti
manasā prastauti | manasādimādatte | manasodgāyati manasā pratiharati
manasopadravati | manasā nidhanamupayantyasamāptasya samāptyai
yadvai devā yajñasya vācā na samāpnuvaṃstadasya manasā samāpnuvan
tadyanmanasā stuvantyasamāptasyaiva samāptyai
raso vā etasyāhno'tyanedat
tammanasaiva paryagṛhṇan
eṣa vai sa rasaḥ
tadyanmanasā stuvanti rasasyānatinedāya

They chant on Gāyatrī verses; the Gāyatrī is unexhausted among meters, for the sake of unexhaustedness.
They chant on three [verses]; three indeed are these worlds—to attain these worlds.
Moreover, three are the breaths: expiration, inhalation, and diffused breath.
Having continued these, having become established in them, they attain the conclusion.
The Gāyatra is the sāman; unexhausted indeed is the Gāyatra, for the sake of unexhaustedness.
Moreover, the mind is the Gāyatra.
With the mind alone do they prosper this; with the mind they turn [it]; with the mind they make the him sound;
with the mind he chants the prologue; with the mind he takes up the beginning; with the mind he sings the udgītha; with the mind he responds;
with the mind he sings the upadrava; with the mind they approach the finale, to conclude what is unfinished.
What of the sacrifice the gods could not conclude with speech, that of it they concluded with the mind.
In that they praise with the mind, it is to conclude what is unfinished.
The sap indeed of this day flowed past;
they seized it with the mind alone.
This is indeed that sap.
In that they praise with the mind, it is so that the sap does not flow past.