Bhashya
अथ तदा एनं मृतम् अग्नये अग्न्यर्थमेव अन्त्याहुत्यै हरन्ति ऋत्विजः ; तस्य आहुतिभूतस्य प्रसिद्धः अग्निरेव होमाधिकरणम्, न परिकल्प्योऽग्निः ; प्रसिद्धैव समिन् समिद् ; धूमो धूमः ; अर्चिः अर्चिः ; अङ्गारा अङ्गाराः ; विस्फुलिङ्गा विस्फुलिङ्गाः ; यथाप्रसिद्धमेव सर्वमित्यर्थः ।तस्मिन् पुरुषम् अन्त्याहुतिं जुह्वति ; तस्यै आहुत्यै आहुतेः, पुरुषः भास्वरवर्णः अतिशयदीप्तिमान्, निषेकादिभिरन्त्याहुत्यन्तैः कर्मभिः संस्कृतत्वात्, संभवति निष्पद्यते ॥
In plain words
Now, when the moment comes, the priests carry the dead body to the fire, for the fire's own sake, as the last offering. Here, unlike the four fires before it, nothing needs to be imagined: the actual fire is the actual site of the offering. Fuel is just fuel, smoke just smoke, flame just flame, coals just coals, sparks just sparks -- everything is exactly what it plainly is. Into that fire they offer the man, as the final oblation. And from that offering a person comes to be, radiant, brilliant beyond the ordinary -- because he has been shaped and sanctified by every rite from the very first, at conception, all the way to this last one.
Close to the Sanskrit
Now, at that time, the officiating priests carry this dead person to the fire, for the sake of the fire itself, for the final oblation. Of that [person] who has become the oblation, the well-known, actual fire alone is the site of oblation -- not a fire to be figuratively constructed. The well-known, actual fuel itself is fuel; smoke is smoke; flame is flame; coals are coals; sparks are sparks -- meaning, everything is exactly as it is commonly known. Into that [fire] they offer the man as the final oblation. From that oblation -- from that offering -- a person of radiant hue, possessing exceptional brilliance, comes into being, is produced, because he has been sanctified by the rites beginning with the rite of impregnation and ending with the final oblation.