Imam Khomeini has undertaken serious discussion in this regard in his famous book of “an exposition on Forty Hadith:
Imam explains and sheds light in this regard as following:
Remember that hypocrisy in religious faith is the worst kind of hypocrisy; its retribution also is the severest and its bad effects are far greater and more dangerous than those of other forms of hypocrisy.
One who is guilty of this sin, if he does not believe genuinely in those ideas which he pretends to believe in, is counted among the munafiqun (hypocrites), whose place is in the Fire, and he is doomed to eternal damnation and his punishment is the severest of punishments. But if he believes in them, and for the sake of winning peoples’ hearts and for obtaining worldly honor and dignity he makes an ostentation of them, though he is not reckoned among munafiqun, this kind of hypocrisy will cause the light of faith to fade away from his heart and to make the darkness of infidelity and faithlessness to occupy the domain of his heart.
Because in the first instance this person commits polytheism (shirk) of the covert type; while his religious beliefs and acts should purely be meant for God and His Holy Essence, he is guilty of committing the sin of doing them for others and thus makes them to share what should absolutely belong to Him only. In this way he makes others partners to God and has given permission to the Devil to occupy his heart as if it does not belong to God.
It has been mentioned earlier that faith emerges from the depths of the heart, and in this matter mere abstract knowledge does not suffice. It has been stated in the tradition that any kind of riya’ is polytheism, but this vice, this disastrous atrocity, this hidden cruelty (to one’s own self), and this vicious habit, results in nullifying the good deeds, and in surrender of the realm of the heart to other than God.
The darkness of this vice causes man to leave this world as an unbeliever in God, and the feigned faith that he had assumed proves nothing more than a senseless and empty profession; it is a form without content, a body without soul and a skull without brain; and in no way is acceptable to God. This fact is confirmed by a tradition mentioned in al-Kafi, narrated by ‘Ali ibn Salim:
The narrator of the tradition says that he heard Imam al-Sadiq (A) saying that God Almighty said, “I am the best of friends; one who makes others My partners in any matter, his deeds are not acceptable to Me. I accept only those acts that are purely done for My sake.”
Hence, it is clear that if the spiritual acts (of the heart) are not performed with sincerity of the heart, they will neither be the object of attention of the Almighty, nor will He acknowledge them, and they will be credited in the account of that partner-the person, for whose sake they were performed. Thus the spiritual acts performed for the sake of somebody else, not for God, will surpass the limits of polytheism, and will enter the domain of kufr (infidelity).
It may even be said that the performer of such adulterated acts would be treated as one of the munafiqun.
As his polytheism is not visible, his hypocrisy also is hidden. He, the poor fellow, considers himself to be a believer, whereas in reality he is an idolater, and he is condemned to taste the chastisement prescribed for the munafiqun. How pitiable is the plight of one whose good deeds are to terminate in nifaq.