In Islamic philosophy, the qalb (قلب) or heart is the center of the human personality. The Quran mentions "qalb" 132 times and its root meaning suggests that the heart is always in a state of motion and transformation. According to the Quran and the prophetic tradition, the heart plays a central role in human existence, serving as the source of good and evil, right and wrong. In Islam, God is more concerned with the motives of one's heart than their actions. The heart is also a medium for God's revelations to human beings, and is associated with virtues such as knowledge, faith, purity, piety, love, and repentance. Without purification, however, the heart can become plagued with negative attributes such as sickness, sinfulness, evil, and hate.
Theologically, the heart is regarded as the barzakh or isthmus between this world and the next, and between the visible and invisible worlds, the human realm, and the realm of the Spirit.
The Quran frequently employs the term "qalb" (heart), which appears 132 times, and at times substitutes it with similar terms. The word's root meaning denotes concepts of change, transformation, and fluctuation, implying that the heart is constantly in motion and may undergo reversal or alteration. The Quran uses the term "heart" in various ways that highlight its central role in human existence. These diverse uses of the word imply that its original meaning - involving ideas of turning, changing, and overturning - remains relevant, as the heart is regarded as the source of good and evil, right and wrong. The Quran teaches that both believers and non-believers possess hearts. In general, the Quran portrays the heart "as the locus of that which makes a human being human, the center of the human personality". This importance of the heart is due to the profound relationship between humans and God, with the heart being the point of convergence where they can meet God. This interaction is multi-dimensional, encompassing both cognitive and moral dimensions.