Vishnupurana 3.15.29

3.15.29

tato 'nnaṃ mṛṣṭam atyartham abhīṣṭam atisaṃskṛtam
dattvā juṣadhvam icchāto vācyam etad aniṣṭhuram //

"The sacrificer is then to offer food, without salt or seasoning, to fire, three several times, with the consent of the assistant Brahmans; exclaiming first, 'To fire, the vehicle of the oblations; to the manes Swáhá!' Next addressing the oblation to Soma, the lord of the progenitors; and giving the third to Vaivaswata. He is then to place a very little of the residue of the oblation in the dishes of the Brahmans; and next, presenting them with choice viands, well dressed and seasoned, and abundant, he is to request them civilly to partake of it at their pleasure. The Brahmans are to eat of such food attentively, in silence, with cheerful countenances, and at their ease. The sacrificer is to give it to them, not churlishly, nor hurriedly, but with devout faith.