As per Shrimad Bhagavatam, a Chandala becomes as pure as a brahmana simply by chanting or hearing the Holy Names of Lord Vishnu, offering obeisance unto Him or just by remembering Him.
यन्नामधेयश्रवणानुकीर्तनाद्
यत्प्रह्वणाद्यत्स्मरणादपि क्वचित् ।
श्वादोऽपि सद्य: सवनाय कल्पते
कुत: पुनस्ते भगवन्नु दर्शनात् ॥ ६ ॥
yan-nāmadheya-śravaṇānukīrtanād
yat-prahvaṇād yat-smaraṇād api kvacit
śvādo ’pi sadyaḥ savanāya kalpate
kutaḥ punas te bhagavan nu darśanāt
Translation: To say nothing of the spiritual advancement of persons who see the Supreme Person face to face, even a person born in a family of dog-eaters immediately becomes eligible to perform Vedic sacrifices if he once utters the holy name of the Supreme Personality of Godhead or chants about Him, hears about His pastimes, offers Him obeisances or even remembers Him.
Source: https://vedabase.io/en/library/sb/3/33/6/