What did Ibn al-Qayyim say about the heart?

"to will. Among those who truly know, longing for treachery and occupying the thought and the heart with it is more harmful to the heart than the treachery itself — especially when the heart is emptied of it after it has been committed — for longing for it keeps the heart busy with it, fills the heart with it, and makes it the heart's whole concern and object. You see this plainly in the visible world: when a human king has among his retinue and servants one who longs to betray him, his heart and thought occupied with it and brimming with it, while for all that he is in the king's service attending to his affairs — then, when the king learns of his secret and intent,"

"at it until the heart is present, so that the two go together in the remembrance. Others see it otherwise and will not begin while heedless; rather they grow still until the heart is present, then set out in remembrance with the heart, and when it grows strong it draws the tongue along after it, so that the two go together. The first transfers the remembrance from his tongue to his heart; the second transfers it from his heart to his tongue without his heart ever being empty of it."

"Imam Ahmad related from Hudhaifa ibn al-Yaman, may Allah be pleased with him, who said, The hearts are of four types. A heart that is clear with a lamp glowing, which is the heart of the believer. A heart that is sealed, which is the heart of the disbeliever. An overturned heart, which is the heart of the hypocrite. And a heart that is supplied by two materials, material of faith and material of hypocrisy, determined by which of them prevails."

"it never entirely escapes dullness. The Prophet, peace be upon him, said, Hearts are four, a pure heart with a radiant lamp within it, and this is the heart of a believer, a black, overturned heart, which is the heart of a disbeliever, a sealed heart bound upon its seal, which is the heart of a hypocrite, and a heart layered with faith and hypocrisy."

"the Exalted. The Hadith states, If God intends good for His servant, He places a preacher in his heart, as reported by Abu Mansur al-Daylami from Umm Salama. The Prophet, peace be upon him, also said, He who has a preacher in his heart has a protector from God. Another Hadith reported by Ahmad and al-Tabarani states, The heart of the believer is clear, a brilliant lamp is within it. Obedience to Allah by opposing desires polishes the heart, while sins darken it. Whoever turns to sins blackens their heart, but whoever follows an evil deed with a good one that erases it does not have an unjust heart. However,"

"This water would be purer, more lasting, and possibly more copious. In the same way, the heart is like a basin, knowledge is like water, and the five senses are like the channels. Knowledge can be conveyed to the heart through the channels of the senses, influenced by what is observed, until it is filled with knowledge. Or, these channels may be blocked by solitude, isolation, and lowering the gaze, while penetrating the depth of the heart by purifying it and removing layers of obstructions until the springs of knowledge burst from within. If you ask how knowledge erupts from the heart itself when it is void, know that this is one of the wondrous secrets of the heart."

"Peace be upon him. If Allah intends good for a servant, he places within his heart a preacher. This implies that the heart becomes enriched with divine remembrance, as Allah stated. Indeed, it is in the remembrance of Allah that hearts find rest. The blameworthy effects of sin are like dark smoke that rises to cover the heart's mirror, layer by layer, until the heart becomes completely obscured from Allah. This results in the heart being sealed or rusted, as described in the Quran. No, rather, what they earn has covered their hearts. In another verse, Allah says, If we willed, we would afflict them for their sins and seal their hearts so they will not hear."

"So the servant turns his face wholly toward Him, and comes forward with his heart, his spirit, and his every care; he surrenders to Him alone, outwardly and inwardly, and his secret and his open state become one. Then he says, there is no god but God, sincerely from his heart, his heart now freed from attachment to anything else and from any glance toward what is other than Him. The whole world has gone out of his heart, he is on the threshold of arriving before his Lord, the fires of his desire have died down, and his heart is filled with the Hereafter, so that it stands before his very eyes while the world lies behind his back. Thus that pure testimony becomes the seal"

"is granted, then how about he who neglects? These are summaries of what should be preserved from your outward faculties. The actions of these limbs only spring from the heart's traits. If you wish to preserve the faculties, then purify the heart first, that is, the inner piety. The heart is the flesh that if sound, the body is sound by it, and if corrupted, the whole body is corrupted. So work on its correction for your faculties, preservation. It is corrected by constant vigilance. On the sins of the heart, know that the reprehensible traits of the heart are many, and the path to its purification from these vices is long. The means of treatment in this are"

"This is among the noblest types of remembrance. There are five types of remembrance. Sometimes it occurs through both the heart and tongue together, which is the best form. Other times it is through the heart alone, which holds the second rank. Lastly, it can be through the tongue alone, which is the third rank. The best remembrance is when the heart and tongue are in harmony. Chapter The Remembrance of Allah is Superior to Supplication Indeed, the remembrance of the heart alone is superior to the remembrance of the tongue alone. This is because the remembrance of the heart leads to knowledge, stirs love, arouses modesty, inspires fear, calls to vigilance,"