Manava Dharmashastra 5.138

5.138

sāmānyoktaḥ sacchūdrāṇāṃ prasaṃgenāyaṃ dharma ucyate | nyāyavartino dvijaśuśrūṣavo mahāyajñānuṣṭhāyinaśca | tairvapanaṃ muṇḍanaṃ māsikaṃ karttavyam | tṛtīyārthe ṣaṣṭhī | athavā brāhmaṇāśritāstatparatantrāḥ | brāhmaṇaiḥ 'kāryam' | anekārthatvātkaroterupadeṣṭavyamiti pratipattiḥ | vaiśyavat śaucakalpaviśeṣāḥ, sūtakādāvācamane ca | dvijocchiṣṭaṃ ca bhojanaṃ etatprāgvyākhyātam |

Medhātithi’s commentary (manubhāṣya):
A general rule of conduct is here laid down for the better class of Śūdras.

‘Living according to law;’—i.e. attending on twice-born men and performing the great sacrifices. By these ‘shaving’—of the head—shall be done ‘every month’. The Genitive in Śūdrāṇām has the sense of the Instrumental. Or, in as much as śūdras are entirely dependent upon Brāhmaṇas their shaving shall be got done by these latter; and in this case the root ‘kṛ,’ which has several meanings, is to be taken in the sense of advising.

The details of the manner of purification—in connection with births, deaths and the rest—should be like those of the Vaisḥya.

‘Their food shall consist of the leavings, or twice-born men.’—This has been already explained before.—(138).