Imam has in this regard has undertaken very serious discussions in his famous book “an exposition on Forty Hadith”.
According to Imam, It is a matter of pity for a person that his prayers and other devotional acts should serve as fuel for the fires of hell. May God save us from the moment when, in spite of one’s alms-giving and zakat and piety, one’s appearance will be distorted to such hideousness that it is not even imaginable.
You, a helpless creature, are branded as a mushrik, an idolater, and a sinner despite your belief in the Unity of God. God willing, He will forgive the sinners by His mercy, but for the mushrik He has said that He will not forgive him if he dies without repentance, Imam explained.
Pitiable is the condition of the devotees, worshippers, leaders and followers of Friday congregations and men of high knowledge and learning! When they will open their eyes in the court of the Most High on the Day of Judgment, they will come to know that they are not only among the sinners, perpetrators of major sins, but even worse than infidels and idolaters, and their record of deeds even darker than theirs, the late founder of the Islamic Republic explained.
It is stated in the ahadith that one used to Riya’-the one who makes a display of his religiosity, devotion, high religious status, his preaching and leading of prayers, his fasting, his namaz and even his pious deeds for the sake of gaining respect in the hearts of people is a polytheist. His shirk (idolatry) is confirmed by the traditions of the Imams of the Holy Household (A) and the Quranic text, and hence his sin is unpardonable. It would have been better for you to be among the perpetrators of major sins, to be one notorious for his evil conduct and perpetration of obvious indignities, while being a monotheist, instead of becoming a polytheist.