Jaiminīya (Talavakāra) Brāhmaṇa 2-2.9

2-2.9

sa yathā putraḥ pitaramāgatya tata tateti hvayettādṛktat
so vā ubhayarūpā bhavati
tamiti vai puṃso rūpamagruva iti striyai
ubhayamu ha vā etadbhūtvā prajāpatiḥ prajajñe
tadāhurabhyudite vaiṣā pratipat
yoge tvāgate pavasva vāco agriya ityeva pratipatkāryeti
mano vai prajāpatiḥ
mano vai vāco'gram
tadenaṃ tatsvenaiva rūpeṇārabhante
so vai mithunā-bhavati
pavasveti vai puṃso rūpaṃ vāca iti striyai
tadetanmithunaṃ prajananaṃ kriyate
mithunena jāyate ya evaṃ veda
tasmādeṣaiva pratipatkāryā
upāsmai gāyatā nara iti dvitīyā
tadetasmādahno na yanti
davidyutatyā ruceti tṛtīyā pratyakṣametasyāhno rūpam
tamīṃ hinvantyagruva iti caturthī yābhyuditā pratipattāṃ nedantarayāmeti

Just as a son, having come to his father, would call, 'Father, father!' such is that.
It has a dual form:
'tam' is the form of the male; 'agruvaḥ' is of the female.
Having become both of these, Prajāpati brought forth offspring.
Regarding this they say: 'This opening verse is [only] at daybreak.
When the proper time has arrived, "pavasva vāco agriyaḥ" ("Flow, the foremost of speech") should be made the opening verse.'
Mind is Prajāpati;
mind is the forefront of speech.
Thus they begin him in his own form.
It becomes a pair:
'pavasva' is the form of the male; 'vācaḥ' is of the female.
Thus this pair is made productive.
He is born with a pair who knows thus.
Therefore this very one should be made the opening verse.
'upāsmai gāyatā naraḥ' ('Sing unto him, O men') is the second;
thereby they do not depart from this day.
'davidyutatyā rucā' ('With flashing radiance') is the third, the visible form of this day.
'tam īṃ hinvanty agruvaḥ' is the fourth, so that [they say], 'Lest we omit that opening verse which belongs to daybreak.'