Śatapatha Brāhmaṇa ("of a hundred paths") 9.3.4.18

9.3.4.18

taṃ vai madhye pārthānāmabhiṣiñcati | saṃvatsaro vai pārthāni saṃvatsarasyaivainametanmadhyata ādadhāti ṣaṭ purastājjuhoti ṣaḍupariṣṭātṣaḍvā ṛtava ṛtubhirevainametatatsuṣuvāṇamubhayataḥ parigṛhṇāti bṛhaspatiḥ pūrveṣāmuttamo bhavatīndra uttareṣām prathamo brahma vai bṛhaspatiḥ kṣatramindro brahmaṇā caivainametatkṣatreṇa ca suṣuvāṇamubhayataḥ parigṛhṇāti

He anoints him h the middle of the Pârtha oblations, for the Pârtha oblations are the year: he thus places him in the middle of the year. Six he offers before, and six after (the consecration ceremony), for there are six seasons: by the seasons he thus encloses (guards) him who is consecrated on both sides. Brihaspati is the last of the first (six), and Indra the first of the last (six),--Brihaspati is the priesthood (or priestly office), and Indra is the nobility (or political power): by the priesthood and the nobility he thus encloses him who is consecrated on both sides.