Famai yuridil laahu ai yahdiyahoo yashrah sadrahoo lil islaami wa mai yurid ai yudillaho yaj'al sadrahoo daiyiqan harajan ka annamaa yassa' 'adu fis samaaa'; kazaalika yaj'alul laahur rijsa 'alal lazeena la yu'minoon
So whoever Allah wants to guide – He expands his breast to [contain] IsLam; and whoever He wants to send astray – He makes his breast tight and constricted as though he were climbing into the sky. Thus does Allah place defilement upon those who do not believe.
1 Mufti Taqi Usmani
So, whomsoever Allah wills to guide, He makes his heart wide open for Islam, and whomsoever He wills to let go astray, He makes his heart strait and constricted, (and he feels embracing Islam as difficult) as if he were climbing to the sky. In this way, Allah lays abomination on those who do not believe.