Translation by Dr. Muhammad Muhsin Khan & Dr. Taqi-ud-Din al-Hilali
And how can you know that he might become pure (from sins)?
Word by Word — Arabic, Transliteration & Meaning
وَمَاwamāBut what
يُدْرِيكَyud'rīkawould make you know
لَعَلَّهُۥlaʿallahuthat he might
يَزَّكَّىٰٓyazzakkāpurify himself
Tafsir al-Quran al-Karim — Hafiz Abdus Salam Bin Muhammad Bhutvi
Tafsir al-Quran al-Karim is a 4-volume Quran commentary by Hafiz Abdus Salam bin Muhammad Bhutvi, a renowned Salafi (Ahl al-Hadith) scholar and Sheikh ul-Hadith from Pakistan. Based on over 45 years of teaching and research, this tafsir follows the methodology of Tafsir bil-Ma'thur — interpreting the Quran through authentic Hadith, statements of the Companions, and the understanding of the early generations (Salaf). It is distinguished by its complete avoidance of Israeliyyat (Judeo-Christian narratives) and unverified reports. The tafsir is originally written in Urdu, translated to English by tohed.com.
(Ayah 4,3) {وَمَايُدْرِيْكَلَعَلَّهٗيَزَّكّٰۤى … :} The thought you had that this blind man is already a Muslim, he can ask his question some other time, and that I should focus more on converting the disbeliever to Islam—although this is correct to some extent, it was also necessary for you to consider that the disbeliever was not even willing to benefit from your guidance. Treating a person suffering from a dangerous illness should take precedence, but if he is not willing to take the medicine, then why should you neglect your companions in hopes for him, who are seekers of the medicine for the heart, so that if you pay attention to them, they will become thoroughly purified from ignorance and sin. In {’’ يَزَّكّٰۤى ‘‘} there is exaggeration, or that he may benefit from your advice.