Verse 3.16.5

अथ यान्यष्टाचत्वारिंशद्वर्षाणि तत्तृतीयसवनमष्टाचत्वारिंशदक्षरा जगती जागतं तृतीयसवनं तदस्यादित्या अन्वायत्ताः प्राणा वावादित्या एते हीदंसर्वमाददते ॥ ३.१६.५ ॥

atha yānyaṣṭācatvāriṃśadvarṣāṇi tattṛtīyasavanamaṣṭācatvāriṃśadakṣarā jagatī jāgataṃ tṛtīyasavanaṃ tadasyādityā anvāyattāḥ prāṇā vāvādityā ete hīdaṃsarvamādadate || 3.16.5 ||

5. Then the next forty-eight years are the third libation. The jagatī metre has forty-eight syllables, and the third libation is accompanied by a hymn which is in the jagatī metre. The Ādityas are connected with this third libation. The prāṇas are called Ādityas because they accept [ādā] all things.

Word-for-word explanation:

Atha, next; yāni aṣṭācatvāriṃśat varṣāṇi, that which is the next forty-eight years; tat, that; tṛtīya savanam, is the third libation; jagatī aṣṭācatvāriṃśat akṣarā, the jagatī metre is constituted of forty-eight syllables; jāgatam tṛtīya savanam, the third libation is accompanied by a hymn in the jagatī metre; asya, of this [i.e., this sacrifice of the human body]; tat, it [the third libation covering the next forty-eight years];

ādityāḥ, the deities called Ādityas; anvāyattāḥ, are connected; prāṇāḥ vāva ādityāḥ, the prāṇas are the Ādityas; hi, for; ete, these [Ādityas]; idam sarvam ādadate, accept [ādā] all objects.

Commentary:

A human being is supposed to live a total of a hundred and sixteen years, which has three phaṣes: the first twenty-four years, the next forty-four years, and the last forty-eight years. When this life is thought of as a sacrifice, the first twenty-four years would be the morning offering, the next forty-four years would be the midday offering, and the last forty-eight years would be the evening offering.

Just as the morning libation is connected with the Vasus, so the first twenty-four years of one’s life are also connected with the Vasus. The gāyatrī is sung during the morning offering, and it has twenty-four syllables. The offering made at midday is connected with the Rudras, and it is accompanied by a hymn in the triṣṭubh metre, having forty-four syllables. Then the evening offering is connected with the Ādityas, and it is sung in the jagatī metre, having forty-eight syllables. The concept of a human life as a sacrifice arises from the similarity to the components of a ritualistic sacrifice.