Aśauca-vidhi (Rules of Impurity) within Śrāddha-kalpa — Chapter on Testing/Selecting Brahmanas and Honoring the Atithi
नाव्रती न च संकीर्णो नाविद्यो नाविशेषवित् / न च संतानसंबद्धो न देवी नागसे ऽतिथिः
nāvratī na ca saṃkīrṇo nāvidyo nāviśeṣavit / na ca saṃtānasaṃbaddho na devī nāgase 'tithiḥ
An atithi is not one without vows, nor one of tainted conduct; not the ignorant, nor one who knows no proper distinctions; not a kinsman of one’s own lineage, not a goddess, and not a sinner—such is not called an atithi.