Vyasasmriti 1.6

1.6

śūdrovarṇaścaturtho'pi varṇatvāddharmamarhati
vedamantrasvadhāsvāhāvaṣaṭkārādibhirvinā

The Śūdra, though the fourth social class, is entitled to socio-religious duty by virtue of being a social class,
except for Vedic mantras, svadhā, svāhā, the vaṣaṭ utterance, and the like.