What is the significance of latif (spiritual parts of human self)? Do they find a mention in the Qur'an?
The Holy Qur'an refers to a nafs-i lawwamah, the spiritual aspect of a human being nafs. The Book also employs the expression fu'ad or qalb for this entity. On the basis of this, Muslims scholars have believed in that we have a spiritual aspect of our being. Actually the Book uses the words fu'ad and qalb for nafslawwamah figuratively. Nafs lawwamah is basically the faculty of our mind blessed with the following three things:
a. Knowledge of Good and Evil, God and consciousness of test and trial.
b. Freedom to exercise the knowledge of good and evil.
c. Conscience (which censures committing evil)
This nafs lawwamah guides us like a torch where to go. Its light makes us see which path is wrong taking to evil and which is right leading to the truth. It is only our nafs which leads us to righteousness. Otherwise it is impossible to make a list of right and wrong. It is the awareness bestowed upon us by it that always leads us to a quick conclusion in distinguishing good from evil. If we opt to commit an evil it makes us repulse the act. It helps us avoid doing the act. And if we commit an evil ignoring its guidance it rebukes and censures us and thus leads us to repent.
 Q. 75: 2
 Q 17: 36
 Q 7: 179