Kauṣītaki (Śāṅkhāyana) Brāhmaṇa 23.4.32

23.4.32

tad etasya ahno rūpam /

are verses of six Padas; the year has six seasons; verily (they serve) to obtain the year. ‘They are to be recited as Gāyatrī verses’, Kauṣītaki used to say; the reciting as Gāyatrī makes full completion; in that with each set of eight syllables he says the Praṇava, that is the Gāyatrī form. ‘Indra with the Maruts, the bull, for joy’ is in normal Triṣṭubh and supports the pressing. The explanation of this has been given. It contains (the word) ‘bull’ in ‘The bull, for joy’; this is a symbol of this day. ‘He by whom this’ is the Marutvatīya; it is in Gāyatrī, for this set of three days has the Gāyatrī at the midday pressing.