الَّذينَ آمَنوا وَتَطمَئِنُّ قُلوبُهُم بِذِكرِ اللَّهِ ۗ أَلا بِذِكرِ اللَّهِ تَطمَئِنُّ القُلوبُ

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