A Muslim can appear righteous on the outside while struggling with serious problems on the inside. A person may pray, fast, give charity and read the Qur’an, yet still have a heart affected by envy, arrogance, hatred, showing off or excessive attachment to the dunya.

This is why Islam places great importance on the condition of the heart.

Allah says:

“The Day when there will not benefit [anyone] wealth or children, but only one who comes to Allah with a sound heart.”
Qur’an 26:88–89

The heart in Islam is not simply the physical organ inside the body. It is also connected to a person’s intentions, beliefs, emotions, desires and spiritual condition. What happens inside the heart eventually affects what appears in a person’s words and actions.

One of the most dangerous diseases of the heart is arrogance.

Arrogance can make a person believe that he is better than others because of his wealth, knowledge, appearance, family, position or religious achievements. A person may even become proud of his worship and begin looking down on Muslims who are struggling.

But Islam teaches humility.

The Prophet ﷺ warned about arrogance and explained that it involves rejecting truth and looking down upon people. This means a person can be outwardly successful while spiritually damaging himself through the way he sees others.

Another serious disease is envy.

Envy is more than admiring what someone else has. It is when a person dislikes another person’s blessing and wishes that the blessing would disappear. Someone may become uncomfortable when a friend succeeds, resent a neighbour’s prosperity or secretly hope that another person’s marriage, business or opportunity fails.

The believer should learn to fight this feeling by remembering that Allah distributes His blessings according to His wisdom.

Instead of allowing another person’s blessing to become a source of bitterness, a Muslim can ask Allah for his own blessings and make dua for the person who has been blessed.

There is also the disease of showing off, known as riya.

This happens when a person performs an act of worship partly to be seen, praised or admired by other people. It can be extremely subtle.

Someone may give charity because he genuinely wants to please Allah, but then become more interested in people knowing about his generosity. Someone may pray sincerely but become more careful about his appearance when others are watching.

This is why sincerity requires constant attention.

The believer should regularly ask himself: If nobody knew I had done this, would I still do it for Allah?

Another disease of the heart is love of worldly possessions when that love becomes excessive.

Islam does not forbid wealth, success or enjoying lawful blessings. The problem arises when the dunya becomes more important to a person than his relationship with Allah.

A person can have money without being controlled by money. He can build a successful business without making wealth his ultimate purpose. He can enjoy beautiful things without believing that his value depends on them.

The issue is not necessarily what a person possesses.

It is what possesses his heart.

Hatred and resentment can also damage the heart.

Sometimes a person carries an old disagreement for years. Someone offended him, embarrassed him, betrayed him or treated him unfairly, and the memory continues to influence his relationship with that person long after the incident has passed.

Islam encourages forgiveness and reconciliation, although forgiveness does not mean allowing people to continue harming you.

A Muslim should work toward freeing the heart from unnecessary hatred while still dealing wisely with injustice and protecting legitimate rights.

Another problem is having a good opinion of oneself while constantly judging others.

A person may see his own mistakes as minor while treating someone else’s mistakes as proof that the other person is a bad Muslim. This can lead to self-righteousness.

We do not know what is inside another person’s heart, nor do we know the struggles they are facing privately.

The person we look down upon today may become closer to Allah tomorrow, while the person who feels spiritually secure today may later fall into a serious trial.

This should make a Muslim humble.

The Prophet ﷺ also taught that the heart has an enormous influence on the rest of a person’s life. In the famous hadith, he explained that there is a piece of flesh in the body which, if it is sound, the whole body is sound, and if it is corrupt, the whole body is corrupt. He identified it as the heart.

This gives us a powerful lesson: religious growth is not only about increasing outward actions. It is also about repairing what is happening inside us.

You can work on your heart by increasing sincere remembrance of Allah, reading and reflecting on the Qur’an, making sincere dua, seeking forgiveness, examining your intentions and recognising your own weaknesses.

You can also pay attention to what triggers negative feelings in you.

If another person’s success immediately makes you uncomfortable, ask yourself why.

If correction makes you angry, ask yourself why.

If you need constant praise, ask yourself why.

If you struggle to forgive, ask yourself what you are holding onto.

These questions are not meant to destroy your confidence. They are meant to help you become honest with yourself.

The heart needs maintenance just as the body does.

We wash our clothes when they become dirty. We clean our homes when they become untidy. We take care of our bodies when something is wrong. Yet the spiritual heart also accumulates problems that need attention.

A Muslim should therefore never become so focused on how he appears to other people that he forgets to examine who he is before Allah.

The real goal is not simply to look religious.

It is to become sincere.

It is to become humble.

It is to become merciful.

It is to become less jealous, less arrogant and less attached to what does not ultimately belong to us.

A sound heart does not mean a person never experiences anger, sadness, jealousy or temptation. It means that when these feelings appear, the believer does not simply surrender to them. He recognises them, seeks Allah’s help and works to correct himself.

That work may happen quietly, without anyone else knowing.

And perhaps that is one of the most important parts of spiritual growth: working on the heart that nobody else can see.