Manava Dharmashastra 3.149

3.149

na brāhmaṇaṃ parīkṣeta daive karmaṇi dharmavit
pitrye karmaṇi tu prāpte parīkṣeta prayatnataḥ //

For a rite sacred to the gods, he who knows the law will not make (too close) inquiries regarding an (invited) Brahmana; but when one performs a ceremony in honour of the manes, one must carefully examine (the qualities and parentage of the guest).