Kaushitakagrihyasutra 1.21.12

1.21.12

yenāvapat savitā kṣureṇa somasya rājño varuṇasya vidvān yena dhātā bṛhaspaterindrasya cāvapacchiraḥ tena brahmāṇo vapatedamasyāyuṣmān dīrghāyurayamastu vīro 'sau iti keśāgrāṇi cchinatti kuśataruṇaṃ ca \12\

With, 'With which razor Savitṛ shaved the head of King Soma and Varuṇa, knowing, with which the Creator shaved the head of Bṛhaspati and of Indra, with that, O brahmins, shave this [head] of his; may this hero [so-and-so] be long-lived, endowed with life,' he cuts the ends of the hair and the young kuśa shoot.