According to the Vedic system, a fire sacrifice is held in order to offer oblations of ghee, grains, fruits, flowers and so on, so that Lord Viṣṇu may eat and be satisfied. The Lord says in Bhagavad-gītā (9.26) :

patraṁ puṣpaṁ phalaṁ toyaṁ yo me bhaktyā prayacchati tad ahaṁ bhakty-upahṛtam aśnāmi prayatātmanaḥ

“If one offers Me with love and devotion a leaf, a flower, fruit or water, I will accept it.” Therefore, all these items may be offered in the sacrificial fire, and Lord Viṣṇu will be satisfied. Similarly, brāhmaṇa-bhojana, feeding of the brāhmaṇas, is also recommended, for when the brāhmaṇas eat sumptuous remnants of food after yajṣa, this is another way that Lord Viṣṇu Himself eats. Therefore the Vedic principles recommend that in every festival or ceremony one offer oblations to the fire and give sumptuous food for the brāhmaṇas to eat. By such activities, a householder may be elevated to the heavenly planets and similar places in the higher planetary systems.