Assalaamu alaykum wa rahmatullaah. I have several questions to ask, Allaah willing. What is considered the heart in Islam? Do we have knowledge about our hearts? Is it the thoughts that come in one's head, or is it something that is unseen except by Allaah? For instance, if I willingly think 'I love Allaah and His messenger', sallallahu 'alayhi wa sallam, does that mean that it is from my heart or not? How do we know if we trully feel it? At the same time, if someone is thinking about something in Islam and makes a mistake in thinking, is it considered a sin? May Allaah reward you.

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger.

The status of the heart in Islam is great; it is enough that Allah looks at the heart of the person [and not at his body or color]. If the heart is good (righteous), then all the body will be righteous, as proven by the hadeeth in which the Prophet said, “Verily, in the body there is a piece of flesh which, if it is sound, the whole body is sound, and if it is corrupt, the whole body is corrupt. Verily, that piece of flesh is the heart.” [Al-Bukhaari and Muslim]

As regards the reality of the heart and its essence, then the heart is a creature like all other creatures, and it is not the soul. Rather, scholars define the heart as a spiritual, divine subtle element that has a relation with the physical heart; it is only Allah Who knows how this relation is.

Al-Munaawi, while explaining the hadeeth, said:

“‘Verily, the hearts are between two fingers of the Most Merciful': the hearts, i.e. the hearts of the children of Adam, and this does not mean the pine-shaped piece of flesh that is located in the left side of the chest, because this flesh is also found in animals; rather, it is a spiritual, divine subtle element that is related to the physical heart. This divine subtle element is the reality of the human being; it is the element that perceives, that is addressed, that is required (to perform obligations), and that is punished.

This divine subtle element has a relation with the physical heart, and many people are puzzled as to how they are related, and also about the fact that its relation with it is similar to the relation of accidents with the bodies, the relation of descriptions with what is described, the relation of the one who uses an instrument with that instrument, or the relation of a person occupying a place with that place; and achieving the relation is related to the sciences of Mukaashafah (mystic intuition and apprehension) and not to theoretical sciences.”

If you come to know the essence of the heart and that it is this divine subtle element that is related to the known heart, then the good matters a person thinks of is evidence of the soundness of his heart and that his heart is upright.

Therefore, a person should preoccupy his heart and his thoughts with what will benefit him, such as thinking about the love of Allah and His Messenger and similar matters that will increase the faith in his heart and make it firm, and he should avoid dispraised thoughts that would make him deviate from righteousness and from the straight path. He should endeavor to guard his thoughts, because guarding one’s thoughts is what the righteous people cared for the most.

We know about our hearts by looking at the thoughts that we have. A person may know about the condition of his heart and whether it is sound or sick by looking at what he thinks of and what his heart orders his body parts to do. The heart is the king, and the body parts are the soldiers that carry out his orders. The existence of good thoughts is evidence of the soundness of the heart.

As regards the bad thoughts and what contradicts the religion, then a person is not held accountable for them if these are just internal. It is indeed from the mercy of Allah with His slaves that He forgives them for the internal thoughts that they have as long as they do not act according to them or speak about them. Please refer to fatwa 21800.

Allah knows best.