Agniveshyagrihyasutra 2.7.8.4

2.7.8.4

apa upaspṛśyāṅguṣṭhānāmikābhyāṃ dakṣiṇakarṇamupaspṛśet yadi mūtraṃ kuryāt pādau prakṣāḷyācamya oṃkāraṃ manasā dhyātvā śucirbhūtvā puruṣa evedam̐ sarvam iti dve ṛcau japet \

Having touched water, one should touch the right ear with the thumb and ring finger. If one should urinate, having washed both feet, having sipped water, having meditated in mind on the syllable Om, having become pure, one should mutter the two verses: "Puruṣa evedaṃ sarvam …".