Verse 3.17.5

तस्मादाहुः सोष्यत्यसोष्टेति पुनरुत्पादनमेवास्य तन्मरणमेवावभृथः ॥ ३.१७.५ ॥

tasmādāhuḥ soṣyatyasoṣṭeti punarutpādanamevāsya tanmaraṇamevāvabhṛthaḥ || 3.17.5 ||

5. Therefore people say, ‘He will give birth,’ or ‘He has given birth.’ In either case, it is a rebirth [in the sense that when he starts living his life as a sacrifice, that is his rebirth]. When death overtakes him, that is the conclusion of the sacrifice.

Word-for-word explanation:

Tasmāt, therefore; āhuḥ, it is said; soṣyati, will give birth to; asoṣṭa iti, has given birth to; punaḥ utpādanam eva, [because] it is a rebirth; tat maraṇam eva asya, the death of the person; avabhṛthaḥ, is the conclusion of the sacrifice.

Commentary:

Life is a kind of sacrifice, but when a person dedicates his life as such, he is said to be reborn. The words soṣyati and asoṣṭa are used when a mother is about to give birth, or has given birth, to a child. But they are also used at the time when someone is about to begin performing a sacrifice (soṣyati), or has already begun performing it (asoṣṭa), because it is his rebirth.

When death comes to the person who treats his life as a sacrifice, it is the end of the sacrifice, just as it is the end of his life. Just as aṭ the end of a sacrifice, a person bathes and puts on new clothes, so also, when a person dies, his body is bathed and new clothes are put on it. The treatment is the same, whether the sacrifice is that person’s life or it is the usual sacrificial ritual. And the words used on both occasions are the same. This makes the similarity between the ritualistc sacrifice and life as a sacrifice more meaningful.