Surah Al-An'am (The Cattle), Verse 125

فَمَنْ یُّرِدِ اللّٰهُ اَنْ یَّهْدِیَهٗ یَشْرَحْ صَدْرَهٗ لِلْاِسْلَامِ وَمَنْ یُّرِدْ اَنْ یُّضِلَّهٗ یَجْعَلْ صَدْرَهٗ ضَیِّقًا حَرَجًا كَاَنَّمَا یَصَّعَّدُ فِی السَّمَآءِ كَذٰلِكَ یَجْعَلُ اللّٰهُ الرِّجْسَ عَلَی الَّذِیْنَ لَا یُؤْمِنُوْنَ ۟

Famai yuridil laahu ai yahdiyahoo yashrah sadrahoo lil islaami wa mai yurid ai yudillahoo yaj'al sadrahoo daiyiqan harajan ka annamaa yassa' 'adu fis samaaa'; kazaalika yaj'alul laahur rijsa 'alal lazeena laa yu'minoon

“Those whom Allah (in His plan) willeth to guide,- He openeth their breast to Islam; those whom He willeth to leave straying,- He maketh their breast close and constricted, as if they had to climb up to the skies: thus doth Allah (heap) the penalty on those who refuse to believe.”

Quran 6:125 (Yusuf Ali Translation)