Charak Samhita
शूद्रा तु नमस्कारमेव कुर्यात् (देवाग्निद्विजगुरुतपस्विसिद्धेभ्यः [४] ) ॥१३॥
॥ Rituals for those belonging to the "shudra" lineage॥ Those belonging to shudra lineage, the mere act of salutation/pray (to the God, holy fire, brahmanas, teachers/elders/preceptors, and saints and seers) should suffice.
english translation
zUdrA tu namaskArameva kuryAt (devAgnidvijagurutapasvisiddhebhyaH [4] ) ॥13॥
hk transliteration by Sanscript