Manava Dharmashastra 3.122

3.122

'jñānena' vidyayā 'utkṛṣṭaḥ' adhikaḥ tasmai deyāni kavyāni | ayamaso hastarudhiradigdhopamārthaḥ | rudhiradigdhau hastau rudhireṇopamṛjyamānāvadhikataraṃ rajyete, na nirmalau bhavataḥ, evamavidvān brāhmaṇaḥ bhojyamānaḥ pitṝnadho nayatitarām |

Offerings for gods and Pitṛs should be given to one who is distinguished by knowledge; for hands smeared with blood are not cleansed by blood.—(132)

Medhātithi’s commentary (manubhāṣya):
One who is ‘distinguished’—who excels—‘by knowledge’—in learning; to such a one ‘should be given’ ‘the offerings for gods and Pitṛs.’

The sense of the metaphor of the ‘hand smeared with bloo’ is as follows:—‘Hands smeared with blood when washed with blood only become all the more reddened, and they are not cleansed; similarly, the ignorant Brāhmaṇa, when, fed, only carries the ancestors to still worse hells,’—(132)