Jaiminīya (Talavakāra) Brāhmaṇa 2-8.438

2-8.438

tasyaitau ślokāvayujo yuktāḥ pravahantyagre tato yugmanto anusaṃvahanti
ta ekaṃ chandobhissaṃvatsaramā dvādaśa parisarpanti māsaḥ
dvādaśasya māsa uttame'hanṣaṭtriṃśaṃ ha dadhrire vyāvṛtā ekaṃ
tato yugmabhirvyayuñjatādhyanya āyansuvaranye parāyan
iti
tasya dvādaśa stotrāṇi bhavanti
tenāgniṣṭomaḥ
tānyu eva dvādaśa santi pañcadaśa caturviṃśāni stotrāṇi bhavanti
tenokthyaḥ
sa vā eṣo'gniṣṭomassannukthya ukthyassannagniṣṭomaḥ
ubhau ha tau kāmāvupāpnoti yaścāgniṣṭome yaścokthye ya evaṃ veda

Regarding this, there are these two verses:
'Yoked as odd, they carry forward at the beginning; then, with even [numbers], they carry along.
With the meters, they creep through one year, up to twelve months.
On the last day of the twelfth month, they held a thirty-six-[fold stoma], distinguished as one.
Then they unyoked with even [stomas]; some went up to heaven, others departed.'
It has twelve stotras;
thereby it is an Agniṣṭoma.
And being those twelve, they become fifteen [and] twenty-four stotras;
thereby it is an Ukthya.
It, being an Agniṣṭoma, is an Ukthya; being an Ukthya, it is an Agniṣṭoma.
Whoever knows this obtains both of those desires: that which is in the Agniṣṭoma and that which is in the Ukthya.