Apastambadharmasutra 2.3.7

This reception of guests is an everlasting (Srauta)-sacrifice offered by the householder to Pragâpati.

The fire in the stomach of the guest (represents) the Âhavanîya, (the sacred fire) in the house of the host represents the Gârhapatya, the fire at which the food for the guest is cooked (represents) the fire used for cooking the sacrificial viands (the Dakshinâgni).

He who eats before his guest consumes the food, the prosperity, the issue, the cattle, the merit which his family acquired by sacrifices and charitable works.

Food (offered to guests) which is mixed with milk procures the reward of an Agnishtoma-sacrifice. Food mixed with clarified butter procures the reward of an Ukthya, food mixed with honey the reward of an Atirâtra, food accompanied by meat the reward of a Dvâdasâha, (food and) water numerous offspring and long life.

It is declared in the Veda, 'Both welcome and indifferent guests procure heaven (for their host).'

When he gives food in the morning, at noon, and in the evening, (these gifts) are the Savanas (of that sacrifice offered to Pragâpati).

When he rises after his guest has risen (to depart), that act represents the Udavasânîyâ ishti (of a Vedic sacrifice).

When he addresses (the guest) kindly, that kind address (represents) the Dakshinâ.

When he follows (his departing guest, his steps represent) the steps of Vishnu.

When he returns (after having accompanied his guest), that (act represents) the Avabhritha, (the final bath performed after the completion of a sacrifice.)

Thus (a Brâhmana shall treat) a Brâhmana, (and a Kshatriya and a Vaisya their caste-fellows.)

If a guest comes to a king, he shall make (his Purohita) honour him more than himself.

If a guest comes to an Agnihotrin, he himself shall go to meet him and say to him: 'O faithful fulfiller of thy vows, where didst thou stay (last night)?' (Then he offers water, saying): 'O faithful fulfiller of thy vows, here is water.' (Next he offers milk or the like, saying): 'O faithful fulfiller of thy vows, may (these fluids) refresh (thee).'

(If the guest stays at the time of the Agnihotra, he shall make him sit down to the north of the fire and) murmur in a low voice, before offering the oblations: 'O faithful fulfiller of thy vows, may it be as thy heart desires;' 'O faithful fulfiller of thy vows, may it be as thy will is;' 'O faithful fulfiller of thy vows, may it be as thy wish is;' 'O faithful fulfiller of thy vows, may it be as thy desire is.'

If a guest comes, after the fires have been placed (on the altar), but before the oblations have been offered, (the host) himself shall approach him and say to him: 'O faithful fulfiller of thy vows give me permission; I wish to sacrifice.' Then he shall sacrifice, after having received permission. A Brâhmana declares that he commits a sin if he sacrifices without permission.

He who entertains guests for one night obtains earthly happiness, a second night gains the middle air, a third heavenly bliss, a fourth the world of unsurpassable bliss; many nights procure endless worlds. That has been declared in the Veda.

If an unlearned person who pretends to be [paragraph continues] (worthy of the appellation) 'guest' comes to him, he shall give him a seat, water, and food, (thinking) 'I give it to a learned Brâhmana.' Thus (the merit) of his (gift) becomes (as) great (as if a learned Brâhmana had received it).