tat — of that sacrifice; śeṣeṇa — by the remnants; upajīvanti — they sustain their lives; tri-varga — consisting of the three aims of human life (religiosity, economic development and sense gratification); phala-hetave — for the sake of fruit; puṁsām — for persons; puruṣa-kārāṇām — engaged in human endeavor; parjanyaḥ — Lord Indra; phala-bhāvanaḥ — the means of effecting the intended goals.
By accepting the remnants of sacrifices performed to Indra, people sustain their lives and accomplish the threefold aims of religiosity, economic development and sense gratification. Thus Lord Indra is the agent responsible for the fruitive success of industrious people.
One might object that people sustain themselves by farming, industry and so on. But as previously mentioned, all human and nonhuman endeavor depends on food and drink, which cannot be produced without ample rain. By the word tri-varga Nanda further points out that the prosperity achieved through sacrifice for Indra is meant not merely for sense gratification but also for religiosity and economic development. Unless people are well fed, it is difficult for them to execute their duties, and without performance of duty, it is very difficult to be religious.