Imam Khomeini in his famous book "An exposition on Forty Hadith" explains and sheds the light as following:
They are of enormous benefits for us.
Here we shall mention three of them: they are, al-quwwah al-wahmiyyah-the power of invention or imagination, al-quwwah al-ghadabiyyah-the power of passion or anger, and al-quwwah al-shahwiyyah-the power of lust or sensuality.
Each of these powers is of great benefit to the mankind, like the preservation of the human individual and species, advancement of human interests in this world as well as in the Hereafter, of which religious scholars have given elaborate accounts and I need not repeat them. What is essential to state here is that these three powers are the source and origin of all virtuous and vicious deeds, and the source of all invisible and sublime forms.
Accoding to Imam, as man possesses a physical and a terrestrial form in this world, which is devised and contrived by the Almighty in such a wonderful manner that all great philosophers and scientists are puzzled, and the science of anatomy is not fully equipped to discover and understand its functioning rightly even to this day.
God has made man superior to other living beings by endowing him a superb constitution and a beautiful appearance. Yet there is another form and a different face of him, which is heavenly and invisible, which is determined by the qualities of his soul and his inner nature.
In the Hereafter, whether it is in the Barzakh (an interval of time between the death of man and his resurrection) or whether on the Last Day, if one’s inner nature, his deeds, and his inner self are really human, his heavenly visage also will be man-like.
But if his deeds are inhuman, he will not possess human form; it will be rather subject to the state of his inner self and his psyche. For instance, if his inner self is dominated by the power of lust or sensuality (al-quwwah al-shahwiyyah) and animality and brutality overwhelm and govern his inner self, his otherworldly visage will be of a brute and the reign of his inner world would be under the control of one of the beasts, corresponding to that quality of his soul.
If the power of passion or anger conquers one’s inner self and his psyche, his otherworldly appearance will resemble one of the bestial forms, corresponding to that attribute of his nature.
And if the power of imagination and invention is governed by fiendish forces and his inner self is made vicious, governed by the vices like deceit, dishonesty, slandering, backbiting, which are the attributes of Satan, he may undergo a metamorphosis and assume one of the forms of Satan.
Sometimes it is also possible that he would have an appearance that symbolizes two or several vices. In that case, a form which does not resemble any of the brutes, but an unusual and queer form, with which cannot be compared the most terrible and ugliest monster in the world, will be acquired by him.
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