Aitareya Āraṇyaka 3.2.6

3.2.6

atha hāsmā etat kṛṣṇahārito vāgbrāhmaṇam ivopodāharati \
prajāpatiḥ prajāḥ sṛṣṭvā vyasraṃsata saṃvatsaraḥ \
sa chandobhir ātmānaṃ samadadhād.
yac chandobhir ātmānaṃ samadadhāt, tasmāt saṃhitā \
tasyai vā etasyai saṃhitāyai ṇakāro balaṃ, ṣakāraḥ prāṇa ātmā \
sa yo haitau ṇakāraṣakārāv anusaṃhitam ṛco veda, sabalāṃ saprāṇāṃ saṃhitāṃ veda-.
-āyuṣyam iti vidyāt \
sa yadi vicikitset saṇakāraṃ bravāṇī3ṁ aṇakārā3ṁ iti, saṇakāram eva brūyāt; saṣakāraṃ bravāṇī3ṁ aṣa/kārā3ṁ iti, saṣakāram eva brūyāt \
te yad vayam anusaṃhitam ṛco 'dhīmahe, yac ca māṇḍūkeyam adhyāyaṃ prabrūmas, tena no ṇakāraṣakārā upāptāv iti ha smāha hrasvo māṇḍūkeyaḥ \
atha yad vayam anusaṃhita/m ṛco 'dhīmahe, yac ca māṇḍūkeyīyam adhyāyaṃ prabrūmas, tena no ṇakāra/ṣakārā upāptāv iti ha smāha sthaviraḥ śākalyaḥ \
etad dha sma vai tad vidvāṃsa āhur ṛṣayaḥ kāvaṣeyāḥ.
kimarthā vayam adhyeṣyāmahe.
kimarthā vayaṃ yakṣyāmahe.
vāci hi prāṇaṃ juhumaḥ, prāṇe vā vācaṃ.
yo hy eva prabhavaḥ, sa evāpyayaḥ \
tā etāḥ saṃhitā nānantevāsine prabrūyān, nāsaṃvatsaravāsine, nāpravaktra ity ācāryā, ācāryāḥ \\ 6 \\
\\ ity aitareyatṛtīyāraṇyake dvitīyo 'dhyāyaḥ \\
iti tṛtīyāraṇyakaṃ samāptam \\

Next Krishna-Hârita confided this Brâhmana concerning speech to him (his pupil):

Pragâpati, the year, after having sent forth all creatures, burst. He put himself together again by means of khandas (Vedas). Because he put himself together again by means of khandas, therefore (the text of the Veda) is called Samhitâ (put together).

Of that Samhitâ the letter n is the strength, the letter sh the breath and self (Âtman).

He who knows the Rik verses and the letters n and sh for every Samhitâ, he knows the Samhitâ with strength and breath. Let him know that this is the life of the Samhitâ.

If the pupil asks, 'Shall I say it with the letter n or without it? 'let the teacher say, 'With the letter n.' And if he asks, 'Shall I say it with the letter sh or without it?' let the teacher say, 'With the letter sh.'

Hrasva Mândûkeya said: 'If we here recite the verses according to the Samhitâ (attending to the necessary changes of n and s into n and sh), and if we say the adhyâya of Mândûkeya (Ait. Âr. III, 1), then the letters n and sh (strength and breath) have by this been obtained for us.'

Sthavira Sâkalya said: 'If we recite the verses according to the Samhitâ, and if we say the adhyâya of Mândûkeya, then the letters n and sh have by this been obtained for us.'

Here the Rishis, the Kâvasheyas, knowing this, said: 'Why should we repeat (the Veda), why should we sacrifice? We offer as a sacrifice breath in speech, or speech in breath. What is the beginning (of one), that is the end (of the other).'

Let no one tell these Samhitâs (Ait. Âr. III, 1-III, 2) to one who is not a resident pupil, who has not been with his teacher at least one year, and who is not himself to become an instructor. Thus say the teachers, yea, thus say the teachers.
, and then rest in another place finishing it.