Word by Word Analysis

أَلَمْ تَرَ إِلَى ٱلَّذِينَ يُزَكُّونَ أَنفُسَهُم ۚ بَلِ ٱللَّهُ يُزَكِّى مَن يَشَآءُ وَلَا يُظْلَمُونَ فَتِيلًا 49

Have you not seen those who claim themselves to be pure? Rather, Allāh purifies whom He wills, and injustice is not done to them, [even] as much as a thread [inside a date seed].