Surat Ar-Ra'd (The Thunder) - الرعد

وَيَقُولُ ٱلَّذِينَ كَفَرُوا۟ لَوْلَآ أُنزِلَ عَلَيْهِ ءَايَةٌ مِّن رَّبِّهِۦ قُلْ إِنَّ ٱللَّهَ يُضِلُّ مَن يَشَآءُ وَيَهْدِىٓ إِلَيْهِ مَنْ أَنَابَ ﴿٢٧﴾ ٱلَّذِينَ ءَامَنُوا۟ وَتَطْمَئِنُّ قُلُوبُهُم بِذِكْرِ ٱللَّهِ أَلَا بِذِكْرِ ٱللَّهِ تَطْمَئِنُّ ٱلْقُلُوبُ﴿٢٨﴾

And those who disbelieve say: Why is not a sign sent down upon him by his Lord? Say: Surely Allah makes him who will go astray, and guides to Himself those who turn (to Him). Those who believe and whose hearts are set at rest by the remembrance of Allah; now surely by Allah's remembrance are the hearts set at rest.