Even a Shudra, O goddess, who has purified his soul by pure deeds and who has controlled all his senses, deserves to be waited upon and served with respect as a Brahmana. This has been said by the SelfCreate Brahman himself.
कर्मभिः शुचिभिर्देवि शुद्धात्मा विजितेन्द्रियः। शूद्रोऽपि द्विजवत् सेव्य इति ब्रह्माब्रवीत् स्वयम्॥४८