Bhagavad Gita · Karma YogaChapter 3, Shloka 13 (3.13)

The principle of prasad. First the offering, then the receiving. The food is the same, the attitude is different — and so is the result.

Shankaracharya — "pañca-sūnā". Those who perform the yajña to the gods and so on and eat its remainder — amṛtākhyam (called nectar) — are freed from all sins: cullyādi-pañca-sūnā-kṛtaiḥ — from the sins arising at the "five places of harm", beginning with the hearth, and from harm done unknowingly. (Traditionally, the subtle harm done unknowingly in five household tasks of a householder — the hearth, the grinding stone, the broom, the mortar and pestle, and the water pot — is called "pañca-sūnā".) Those who are ātmambharayaḥ — who only fill their own bellies — and cook for themselves, eat sin.

Acharya Ramanuja: Those who take materials for the worship of the Supreme Person present in the form of Indra and the other gods, cook them, offer worship, and sustain the body with what remains, are freed anādi-kālopārjitaiḥ kilbiṣaiḥ — from sins accumulated from beginningless time, which stand in the way of the vision of the self. Those who cook and eat for themselves the materials the Lord gave for worship eat "agha" — agha-pariṇāmitvād agham — because it turns into sin.