Surah 23. Al-Muminun, Ayah 78

As elsewhere, "heart" is to be understood as the seat both of feeling and intelligence. 'All the means by which knowledge can be gathered, judgment formed, and goodness cultivated, are provided for you by Allah. If you were grateful, you would use those in My service, which is expressed in your service to your fellow men. But instead you ignore these gifts, question Allah's Providence, and blaspheme against Him!'