Kauṣītaki (Śāṅkhāyana) Brāhmaṇa 17.1.4

17.1.4

sa vai harivān bhavati /

xvii. 1. The Ṣoḍaçin is a thunderbolt composed of the Anuṣṭubh; in that they undertake the Ṣoḍaçin, they smite away the evil of the sacrificer with the thunderbolt composed of the Anuṣṭubh. It refers to the 'bay steeds'; the bay is breath, for it draws; therefore it refers to the 'bay steeds'. The Ṣoḍaçin is he yonder that gives heat; verily thus they delight him. There is a sixteenth Stotra, a sixteenth Çastra; therefore is it called the Ṣoḍaçin. In that they undertake the Ṣoḍaçin, and all this (universe) is of sixteen parts, verily (it serves) to obtain all this. Moreover, the Ṣoḍaçin is Indra; therefore it refers to the 'bay steeds', for Indra's bay steeds are praised. 'O Indra rejoice, bring forward, come hither, O hero,