Manava Dharmashastra 3.92

3.92

nātiprasiddho loke'tithiśabdārtha iti tadarthalakṣaṇamāha | ekarātraṃ vasataḥ paragṛhe'titvam | tacca brāhmaṇasya na jātyantare | dvitīye'hni pūjāvidhau kāmacāraḥ | abhyudayaviśeṣāthinastadadhikāraḥ, na naiyamikaḥ | tathā cāpastambaḥ ( 2 |

A Brāhmaṇa staying for a single night has been declared to be a “guest” (Atithi). Because his stay is not long, therefore he is called “Atithi” (guest).—(102)

Medhātithi’s commentary (manubhāṣya):
Inasmuch as the meaning of the term ‘Atithi’ (guest) is not well-known among men, the author provides a definition of the same.

One becomes a ‘guest’ by staying in another man’s house for one night; and this character belongs only to a Brāhmaṇa, to none else.

Whether the next day also the guest should be honoured or not, depends upon the wish of the Householder; it is not. obligatory. It being done by persons desiring prosperity, the incentive to it is something totally different (from that of the obligatory honouring during the first night). Says Apastamba (2.7.16)—‘One should lodge him for one night;’ whereby he wins the regions of the earth; by keeping him on the second night, the regions of the sky; and on the third night, the regions of Heaven”—which shows that the incentive to the entertaining of the guest on the second and following nights consists in the desire for particular rewards.

For the purpose of lending strength to the above explanation, the author provides the etymological meaning—‘His stay is not long; which means that the word ‘atithi’ is derived from the root ‘sthā’ (to stay), preceded by ‘ati;’ the term being formed somehow by the addition of an Uṇādi affix.—(102)