Al-An'am 6:125

Faman yuridi Allahu an yahdiyahuyashrah sadrahu lil-islami waman yurid an yudillahuyajAAal sadrahu dayyiqan harajan kaannamayassaAAAAadu fee assama-i kathalikayajAAalu Allahu arrijsa AAala allatheenala yu/minoon

So whoever Allāh wants to guide - He expands his breast to [contain] Islām; and whoever He wants to send astray - He makes his breast tight and constricted as though he were climbing into the sky. Thus does Allāh place defilement upon those who do not believe.

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.