Mlecchas refer to people who are foreign to India and the Vedic tradition, in contrast to Nastikas who are from India but reject the Vedic tradition. In this excerpt from his Rahasyatraya Sara, the 13th century Sri Vaishnava Acharya Vedanta Desikan discusses a Garuda Purana verse on the subject of how to treat Mlecchas who have become devotees of Vishnu:
"Bhakti or devotion is of eight kinds. If this bhakti is found in a mleccha, he should be considered as a devout and knowing Brahmin. To him giving is proper and from him taking is proper. He should be treated with the same reverence as I myself." This shloka has been commented upon (by Peria Achan Pillai) as meaning not that girls should be given in marriage to him and the like, but that he may be given the gift of knowledge and such like. "Treatment with reverence" is a general term. Therefore it means that if a man has devotion to Bhagavan, he should be treated with as much respect as the shastras permit. Its purport is merely this much, that if a man treats such a devotee in the same way as he would treat others of the same caste, he would go to hell.
I'm interested in the part in bold. For those who don't know, Periyavachan Pillai was a 12th Sri Vaishnava Acharya famous for his commentaries on the Valmiki Ramayana and the Naalayira Divya Prabandham. He was a shishya of Nampillai, whose guru's guru was Parashara Bhattar, Ramanujacharya's successor as the head of the Sri Vaishnava sect. My question is, where in his works does Periyavachan Pillai discuss this verse of the Garuda Purana?
This web page lists his works:
In his life time, he has done vyAkyAnams for:
4000 dhiyva prabhandham – He has written vyAkyAnams for all of aruLicheyal. vyAkyAnams for approximately 400 pAsurams for periyAzhwAr thirumozhi was lost and mAmunigaL just wrote those missing pAsura vyAkyAnams.
sthOthra granthams – He has written vyAkyAnams for pUrvAchArya srisUkthis like sthOthra rathnam, chathu slOki, gadhya thryayam, etc and jithanthE sthOthram.
sri rAmAyaNam – He has selected important slOkams from sri rAmAyaNam and written a detailed commentary for those in rAmAyaNa thani slOki. He was named abhaya pradha rAjar for his masterful explanation of vibhIshaNa sharanAgathi episode.
He has also written many rahasya granthams such as mANikka mAlai, parantha rahasyam, sakala prAmANa thAthparyam, etc which explains rahasya thrayam in an excellent manner. He was a pioneer in documenting rahasya thrayam – piLLai lOkAchAryar took the essence of nampiLLai and periyavAchAn piLLai’s teachings and wrote his astAdhasa rahasya granthams.
As far as I can tell, none of these works have been translated into English, and some may not be available in any form. But the translator was able to identify the person Vedanta Desikan was referring to as Periyavachan Pillai, so it's probably from some available work.
On a side note, does anyone know where in the Garuda Purana this verse occurs? The translator says it's verse "219-6-5", but I'm not sure what that means; the Garuda Purana has three Kandas, each of which have a bunch of chapters, each of which have a bunch of verses. So I don't see how you could specify a verse using three numbers none of which is less than or equal to 3.