According to external vision, Haridasa Thakura belonged to a Muhammadan family. Nevertheless, because he engaged himself in performing the yajna of chanting the Hare Krsna maha-mantra, he became a regularly initiated brahmana. As stated in Srimad-Bhagavatam (3.33.6):

yan-namadheya-sravananukirtanad
yat-prahvanad yat-smaranad api kvacit
svado ‘pi sadyah savanaya kalpate
kutah punas te bhagavan nu darsanat

Even if a devotee comes from a family of dog-eaters, if he surrenders to the Personality of Godhead he immediately becomes a qualified brahmana and is immediately fit to perform yajna, whereas a person born in a family of brahmanas has to wait until completing the reformatory processes before he may be called samskrta, purified…. Haridasa Thakura, although born in a mleccha or yavana family, became Namacarya Haridasa Thakura because he performed the nama-yajna a minimum of 300,000 times every day.

From Srila Prabhupada’s purport to Sri Caitanya-caritamrta Antya-lila 3.124