AR RA'D — Ayat 28

الَّذِينَ آمَنُواْ وَتَطْمَئِنُّ قُلُوبُهُم بِذِكْرِ اللّهِ أَلاَ بِذِكْرِ اللّهِ تَطْمَئِنُّ الْقُلُوبُ

Those who have believed and whose hearts are assured by the remembrance of Allah . Unquestionably, by the remembrance of Allah hearts are assured."