Śatapatha Brāhmaṇa ("of a hundred paths") 2.6.4.6

2.6.4.6

atha yadvaruṇapraghāsairyajate | varuṇenaivaitadrājñā varuṇenānīkenāparāṃścaturo māsaḥ prajayati tattryenī śalalī bhavati lohaḥ kṣurastena parivartayate tadbrahmaṇā caivainametattrayyā ca vidyayā parigṛhṇāti

And when he performs the Varunapraghâsa offerings, he thereby gains other four months, with Varuna for his king, with Varuna for his leader. Then a three-spotted quill of a porcupine and a copper razor are used, wherewith he has himself shaved all round; and thus he (the priest) encompasses him with the Brahman and the threefold science.