"So whoever Allah wants to guide, He expands" — meaning: He widens — "his breast for Islam," "and whoever He wants to misguide, He makes his breast tight and constricted." The meaning of al-haraj (constricted) and al-diq (tight) is the same.
"As if he were climbing into the sky" — meaning: as if he were tasked with ascending to the sky. It means that what he is being called to of faith is heavy upon him.
"Thus does Allah place the impurity" — meaning: the defilement of disbelief — "upon those who do not believe."
