The Ayah: 'Have they not travelled through the land, and have they hearts wherewith to understand'

Q 1: Allah (Glorified and Exalted be He) says (the meanings of which are translated as): Have they not travelled through the land, and have they hearts wherewith to understand and ears wherewith to hear? Verily, it is not the eyes that grow blind, but it is the hearts which are in the breasts that grow blind. Allah (Glorified be He) says in another Ayah (Qur'anic verse): This (Qur’an) is a Message for mankind (and a clear proof against them), in order that they may be warned thereby, and that they may know that He is the only One Ilâh (God - Allâh) - (none has the right to be worshipped but Allâh) - and that men of understanding may take heed. In the first Ayah, which is from Surah Al-Hajj, Allah says that the heart represents the source of reasoning, but in the second Ayah He (Glorified and Exalted be He) says that heedfulness can only be shown by men of understanding, that is, by reason.Why is there a difference between the heart and the mind? Some people take understanding, which Allah attributes to reason as mentioned in the Ayah, as a pretext for refuting Sahih (authentic) Hadiths and making Ta'wil (allegorical interpretation) of them - although they are clearly expressed sometimes and often inconclusive - on the pretext of exercising reason since Allah has praised those who apply reason in many Ayahs. They even claim that accepting the apparent meanings of the Sahih Hadiths (Part No. 3; Page No. 174

A: There is no contradiction between both Ayahs because the source of reason is the heart and it is connected to the brain, as has been declared by the analytical scholars. Sound reason does not contradict with correct Naql (primary Islamic source texts: Qur'an and Hadith). In case there is a contradiction between them, then there is something wrong regarding one of them. Everything that is stated in Nas (Islamic text from the Qur’an or the Sunnah) is understood by reason. Thus, it is obligatory to give precedence to Naql because it is infallible whereas reason is defective and fallible.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.