Jaiminīya (Talavakāra) Brāhmaṇa 1.119

1.119

yo vai yajñasyodharveda duhe yajñam
pavamāno vāva yajñaḥ
tasya gāyatryevodhaḥ
gāyatrīṃ caturṛcāṃ kuryāt
yajñasyaiva tadūdhardadhāti duhe yajñam
yo vai yajñasya pratiṣṭhāṃ veda prati yajñaṃ sthāpayati pratyātmanā tiṣṭhati
pavamāno vāva yajñaḥ
tasya gāyatryeva pratiṣṭhā
gāyatrīṃ caturṛcāṃ kuryādyajñasyaiva tatpratiṣṭhāṃ dadhāti
prati yajñaṃ sthāpayati pratyātmanā tiṣṭhati
uccā te jātamandhasā | asya pratnāmanu dyutam | enā viśvānyarya ā
ityetāsu gāyatraṃ kuryāt
tāsvāmahīyavam
sa yaddhāyyāṃ caturthīṃ dadhāti tena caturṛcaṃ bhavati pratitiṣṭhatībhaḥ
prati yajñaṃ sthāpayati pratyātmanā tiṣṭhati

Whoever knows the udder of the sacrifice milks the sacrifice. The purifying [soma] indeed is the sacrifice; its udder is the gāyatrī. He should make the gāyatrī four-versed. Then he places the udder of the sacrifice [in it]; he milks the sacrifice. Whoever knows the foundation of the sacrifice firmly establishes the sacrifice and stands firm himself. The purifying [soma] indeed is the sacrifice; its foundation is the gāyatrī. He should make the gāyatrī four-versed; then he places the foundation of the sacrifice [in it]. He firmly establishes the sacrifice and stands firm himself. On these [verses]—"Born high with juice...", "According to his ancient brightness...", "By this, all, of the noble..."—he should perform the gāyatra. On them the Āmahīyava. Because he inserts an inserted verse as the fourth, thereby it becomes four-versed, having a foundation. He firmly establishes the sacrifice and stands firm himself.