Vishnupurana 3.15.23

3.15.23

kāle tatrātithiṃ prāptam annakāmaṃ nṛpādhvagam
brāhmaṇair abhyanujñātaḥ kāmaṃ tam api bhojayet //

"Then let the householder, inspired by religious faith, offer oblations to the maternal grandfather, along with the worship of the Viśwadevas, or the ceremony called Vaiśwadeva, which comprehends offerings to both paternal and maternal ancestors, and to ancestors in general. Let him feed the Brahmans who are appropriated to the gods, and to maternal ancestors, with their faces to the north; and those set apart for the paternal ancestors, and ancestors in general, with their faces to the east. Some say that the viands of the Śráddha should be kept distinct for these two sets of ancestors, but others maintain that they are to be fed with the same food, at the same time. Having spread Kuśa grass for seats, and offered libations according to rule, let the sensible man invoke the deities, with the concurrence of the Brahmans who are present. Let the man who is acquainted with the ritual offer a libation to the gods with water and barley, having presented to them flowers, perfumes, and incense. Let him offer the same to the Pitris, placed upon his left; and with the consent of the Brahmans, having first provided seats of Kuśa grass doubled, let him invoke with the usual prayers the manes to the ceremony, offering a libation, on his left hand, of water and sesamum. He will then, with the permission of the Brahmans, give food to any guest who arrives at the time, or who is desirous of victuals, or who is passing along the road; for holy saints and ascetics, benefactors of mankind, are traversing this earth, disguised in various shapes. On this account let a prudent man welcome a person who arrives at such a season; for inattention to a guest frustrates the consequences of an ancestral offering.