وَمَا يُدْرِيكَ لَعَلَّهُۥ يَزَّكَّىٰٓ
Sentence structure
The interrogative clause asks what could make you know. لَعَلَّهُۥ يَزَّكَّىٰٓ is the hoped-for possibility: perhaps he might purify himself.
Ayah summary
Perhaps he would have purified and improved himself through the teaching.
وَمَا — But what
Grammar: وَ is a resumption particle. مَا is an interrogative.
يُدْرِيكَ — would make you know
Grammar: form IV third-person masculine singular imperfect verb; it functions as the predicate. Attached كَ is a second-person masculine singular pronoun functioning as the object.
لَعَلَّهُۥ — that he might
Grammar: لَعَلَّ is a particle resembling a verb and conveys hope or expectation. Attached هُۥ is its noun.
يَزَّكَّىٰٓ — purify himself
Grammar: form V third-person masculine singular imperfect verb; it functions as the predicate of laʿalla.