Mbh 13.90.2a

"'Bhishma said, "The Kshatriya who is conversant with the ordinances about gift should never examine Brahmanas (when making gifts unto them). In all acts, however, that relate to the worship of the deities and the Pitris, an examination has been said to be proper. The deities are worshipped on earth by men only when they are filled with devotion that comes from the deities themselves. Hence, one should, approaching them, make gifts unto all Brahmanas (without any examination of their merits), regarding such gifts as are made to the deities themselves. In Sraddhas, however, O monarch, the man of intelligence should examine the Brahmanas (to be employed for assisting the doers of the Sraddha in getting through the ritual and making gifts unto them of the offerings made to the Pitris). Such examination should concern itself with their birth and conduct and age and appearance and learning and nobility (or otherwise) of parentage. Amongst the Brahmanas there are some that pollute the line and some that sanctify it. Listen to me, O king, as I tell thee who those Brahmanas are that should be excluded from the line.