O God! I testify and bear witness that there is no god but You and that Muhammad (peace be upon him) is Your Prophet and that the Quran is from You and that Your angels and the jinns and the soul exists and that the hereafter and the judgment day and the hellfire and paradise is Truth, and my God, I acknowledge my wrong and immoral sins, and I pray and plead to You that you forgive them, that You show me Mercy, I beg You, God, please, forgive me for my sins! All praise belongs to You and You are the Most worthy of praise, none are worthy of being worshipped except You, You are the King and Protector and Lord and Light and Ruler and Creator of the heavens and the earth and everything in them!
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Onlu a dummy ignorant atheist-materialist would deny the existing of a jinn or a demon.
I have utterly fulfilled God's Command to believe in His angels and the unseen, I don't just believe in it, I know it.
Totally brutalised by Truth, brutalised by God, the King of Truth, that they exists.
+ Total annihilation of ignorance and falsehood on the matter, everything which says that they don't exists, every objection, every argument (that they don't exists), destroyed by Truth, by God, Who is The Trth, the Absolute Truth, and the King of Truth, and the Expeller of ignorance.
*And I have directly experienced and seen and witnessed them (demons, angels, jinns, the soul, spiritual)...
Thus, I have both direct experience and Absolute Knowledge given by God on the matter.
I do this.