Surah Ar-Ra'd, Verse 28

ٱلَّذِينَ ءَامَنُواْ وَتَطۡمَئِنُّ قُلُوبُهُم بِذِكۡرِ ٱللَّهِۗ أَلَا بِذِكۡرِ ٱللَّهِ تَطۡمَئِنُّ ٱلۡقُلُوبُ٢٨

alladhīna āmanū wataṭma-innu qulūbuhum bidhik'ri l-lahi alā bidhik'ri l-lahi taṭma-innu l-qulūbu

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