Hiranyakeshigrihyasutra 2.8.18.9

2.8.18.9

sagaṇaḥ prācīmudīcīṃ vā diśamupaniṣkramya yatrāpaḥ sukhāḥ sukhāvagāhāstadavagāhyāghamarṣaṇena trīnprāṇāyāmānkṛtvā sapavitraiḥ pāṇibhiḥ \ āpo hi ṣṭhā mayobhuvaḥ \ iti tisṛbhiḥ \ hiraṇyavarṇāḥ śucayaḥ pāvakāḥ \ iti catasṛbhiḥ \ pavamānaḥ suvarjanaḥ \ iti caitenānuvākena snātvā darbhānanyonyasmai saṃprayacchanto ditsanta ivānyonyam \9\

(The teacher) with his pupils goes in an easterly or northerly direction, and where they find a pleasant water with a pleasant bathing-place, they dive into it and perform three suppressions of the breath with the Agharmarshana hymn (Rig-veda X, 190 = Taitt. Ar. X, 1, 13. 14.). Holding purifiers (i.e. Darbha blades) in their hands they bathe with the three (verses), 'Ye waters, ye are wholesome' (Taitt. Samh. IV, 1, 5, 1), with the four (verses), 'The gold-coloured, pure, purifying waters' (T.S.V, 6, 1, 1 seq.), and with the Anuvâka, '(Soma) which clears itself, the heavenly being' (Taitt. Br. I, 4, 8): giving the Darbha blades to each other and feigning to try to seize (??) each other.