What is the heart that hardens and softens, in which there is piety, and where is its location?

The heart is not merely a tangible organ; rather, it is an abstract concept that scholars describe as a divine, spiritual essence connected to the physical heart. The nature of this connection is known only to God. Al-Ghazali, Ibn Taymiyyah, and Ibn al-Qayyim all stated that the term "heart" refers to two meanings: first, the physical, pineal-shaped organ of flesh, and second, that spiritual essence which is the true reality of a human being and the seat of perception and knowledge. In the Quran, intellect, understanding, faith, and deviation are attributed to the heart. The heart intended in these verses is located in the chest, and it is that subtle essence connected to the physical organ.