Manava Dharmashastra 3.130

3.130

dūrād eva parīkṣeta brāhmaṇaṃ vedapāragam
tīrthaṃ tad dhavyakavyānāṃ pradāne so 'tithiḥ smṛtaḥ //

Let him make inquiries even regarding the remote (ancestors of) a Brahmana who has studied an entire (recension of the) Veda;
(if descended from a virtuous race) such a man is a worthy recipient of gifts (consisting) of food offered to the gods or to the manes, he is declared (to procure as great rewards as) a guest (atithi).