Apastambagrihyasutra 4.10.5

4.10.5

brāhmaṇānbhojayitvāśiṣo vācayitvā kumāraṃ bhojayitvā 'nuvākasya prathamena yajuṣā 'paḥ saṃsṛjyoṣṇāśśītāsvānīyottarayā śira unatti \ 5 \

(The boy's father) serves food to Brâhmanas and causes them to pronounce auspicious wishes, and serves food to the boy. (The teacher?) pours together, with the first Yagus (of the next Anuvâka, warm and cold) water, pouring the warm water into the cold, and moistens (the boy's) head with the next (verse; M. II, 1, 2).