Imam explains the matter through his theological works as following:
If, God forbid, you want to offend somebody, to slander them or to backbite, you should know that you are in the presence of the Lord; you are to be the guest of God the Almighty, and in the presence of God.
The Supreme, you would behave rudely to one of His servants, and to slander one of the servants of God is to slander God.
They are the servants of God, especially if they are the scholars on the path of knowledge and piety [taqwa]. Sometimes you see that because of such affairs man reaches such a state that he denies God at the moment of his death! He denies the divine signs.
“Then evil was the end of those who did evil, because they rejected the signs of Allah and used to mock them” (Q 30:10).
These things occur gradually. Today, an incorrect view; tomorrow, a word of backbiting; and the next day, slander against a Muslim, and little by little these sins accumulate in the heart, and make the heart black and prevent man from attaining knowledge [ma‘rifat] of Allah, until it reaches the point that he denies everything and rejects the truth, Imam Khomeini further explained.
According to some ayah of the Qur’an as interpreted through some reports, the deeds of men will be presented to the Prophet (s) and the pure Imams (‘a) and will be reviewed by them.
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Morality and character are provisions of human's journey, Imam Khomeini explained