What are hadiths about the heart (the sultan of the bodıly realm)? Examples of hadiths about the heart (the sultan of the bodıly realm)…
ʿĀmir narrated from Nuʿmān b. Bashīr (ra) that the Messenger of Allah (saw) said, “Beware! There is a piece of flesh in the body; if it becomes good (reformed) the whole body becomes good; but if it gets spoilt the whole body gets spoilt and that is the heart.” (al-Bukhari, al-Iman, 39)
Shahr b. Ḥawshab said, “I said to Umm Salama, ‘O Mother of the Believers! What was the supplication that the Messenger of Allah (saw) said most frequently when he was with you?’ She said, ‘The supplication he said most frequently was, “O Changer of the hearts! Make my heart firm upon Your religion.” So I (Umm Salama ) said, ‘O Messenger of Allah! Why do you pray the following supplication so frequently: “O Changer of the hearts! Make my heart firm upon Your religion.” He said, ‘O Umm Salama! Verily, there is no human being except that his heart is between the Two Fingers of the Fingers of Allah; so whomsoever He wills He makes steadfast, and whomever He wills He causes to deviate.’” (al-al-Tirmidhi, al-Daʿawat, 89)
Abu Hurayra (ra) reported that the Messenger of Allah (saw) said, “Verily Allah does not look to your bodies and your wealth, but He looks to your hearts and to your deeds.” (Muslim, al-Birr, 34)
Abu Hurayra (ra) reported that the Messenger of Allah (saw) said, “Verily, when the servant (of Allah) commits a sin, a black spot appears on his heart. When he refrains from it, seeks forgiveness and repents, his heart is polished clean. But if he returns to the sin, the black spot increases until it covers his entire heart. And that is the ‘rān’ which Allah mentioned: ‘No indeed! Their hearts are encrusted (rāna) with what they have done.’” (al-al-Tirmidhi, Tafsīr al-Qurʾān, 83)
ʿAmr b. al-ʿĀṣ (ra) reported that the Messenger of Allah (saw) said, “The heart of the son of Adam has an inclination towards every unworthy desirable thing; so whoever follows all of those inclinations, Allah will not care which of those unworthy desirable things will be the cause of his ruin. And whoever relies upon Allah, Allah will protect him from the pain of scattered inclinations.” (Ibn Maja, al-Zuhd, 14)
Source: Presidency Of Religious Affairs The Turkey, Islam Through Hadiths