Verse 3.6.3.21

athetyāhavanīye samidhamabhyādadhāti | agne vratapāstve vratapā ityagnirhi devānāṃ vratapatistasmādāhāgne vratapāstve vratapā iti yā tava tanūrmayyabhūdeṣā sā tvayi yo mama tanūstvayyabhūdiyaṃ sā mayi yathāyathaṃ nau vratapate vratānyanu me dīkṣāṃ dīkṣāpatiramaṃstānu tapastapaspatiriti tatpratyakṣamagnernirmucyate sa svena satātmanā yajate tasmādasyātrāśnanti mānuṣo hi bhavati tasmādasyātra nāma gṛhṇanti mānuṣo hi bhavatyatha yatpurā nāśnanti yathā haviṣo hutasya nāśnīyādevaṃ tattasmāddīkṣitasya nāśnīyādathātrāṅgulīrvisṛjate

Preview of English translation:

21. He then puts a kindling-stick on the Ahavaniya in this way, “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 of thine hath been on me, (may) that (be) on thee; what bodily form of mine has been on thee, (may) that (be) here on me! Our vows, O lord of vows, (have been performed) rightly: the lord of consecration hath approved my consecration; the lord of penance hath approved my penance.” Thereby he frees himself visibly from Agni, and sacrifices with a self (body) now his own: hence they now partake of his food, for he is a man (again); hence they now use his (real) name, for he is a man. And as to their not eating (of his food) heretofore, it is as one would not eat of sacrificial food, before offering has been made thereof: therefore let no one partake of the food of one consecrated. He now loosens his fingers.

For a detailled translation, including proper diacritics and footnotes, go the full English translation.