The Heart vs The Brain

Shaykh Yasir Qadhi delves into a comparison of the faculties of thought and emotion - the brain and the heart. He goes on to say that if the heart is pure , then the rest of the body is also consequently pure. By ascribing the Iman to our Qalb or heart, Allah signifies its importance. Allah has written directly written Iman into our hearts and it is indeed a great blessing. Allah mentions in the Quran  in Surah Al Hujurat, verses 7 -8: ‘But Allah has endeared to you the faith and has made it pleasing in your hearts and has made hateful to you disbelief, defiance and disobedience. Those are the [rightly] guided. [It is] as bounty from Allah and favor. And Allah is Knowing and Wise.’