What is the relationship between heart and mind?

Question

I need to know the relation between our heart and mind according to Islam.
When we think bad does it has an effect on our spiritual heart and our soul?

Like thinking of kufr shirk and sins. But as far as I know, these thoughts are just passing thoughts that a believer may face. But what if a person all the time feels that negativity is coming from his heart. As I have read the Quran, I came to know that Allah places a lock upon their heart so they cannot think properly. They don't reflect because there is a lock upon their heart.

And I was also reading an article in which it said in order to train your mind to think positive, you have to train purify your heart. Also tell me whether the purification of heart and purification of the soul are the same thing.

Answer 1

A Famous Hadeeth of Muslim

In the human body, there is a small organ. If this organ is tuned, i.e. if this organ is in a good condition, then the whole body would be in a good condition. If not, then the whole body would be in a bad condition; which is the heart.

Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said, “Verily, when the servant commits a sin a black spot appears upon his heart. If he abandons the sin, seeks forgiveness, and repents, then his heart will be polished. If he returns to the sin, the blackness will be increased until it overcomes his heart. It is the covering that Allah has mentioned:

Quran (83:14) No, but on their hearts is a covering because of what they have earned.