Śatapatha Brāhmaṇa ("of a hundred paths") 3.4.3.9

3.4.3.9

sa samidhamabhyādadhāti | agne vratapāstve vratapā ityagnirhi devānāṃ vratapatistasmādāhāgne vratapāstve vratapā iti yā tava tanūriyaṃ sā mayi yo mama tanūreṣā sā tvayi saha nau vratapate vratānīti tadagninā tvacaṃ vipalyaṅgayate 'nu me dīkṣāṃ dīkṣāpatirmanyatāmanu tapastapaspatiriti tadavāntarāṃ dīkṣāmupaiti saṃtarāmaṅgulīracate saṃtarām mekhalām paryastāmevaitatsatīm paryasyate

He puts on the kindling-stick, with the text (Vâg. S. V, 6), 'O Agni, protector of vows; on thee, O protector of vows--' for Agni is lord of vows to the gods; wherefore he says, 'O Agni, protector of vows, on thee, O protector of vows--' 'what bodily form there is of thine, (may that be) here on me; and what bodily form there is of mine, (may that be) on thee! May my vows be bound up with thine, O lord of vows!' whereby he envelops himself with the skin by means of Agni, 'May the lord of consecration approve my consecration, and the lord of penance my penance!' Thereby he enters upon the intermediary consecration. More closely he turns in his fingers, and closer he draws the zone; whereby he (again) puts round himself what was put round him before.