And God Almighty has said: {And God sent him astray despite [his] knowledge}1.
Meaning: God sent him astray despite knowledge he possessed by way of guidance.
And God Almighty only sent him astray after he deserved straying, and We have clarified this in the Chapter of Proving Justice. So they despaired became Iblis-like, and [for] every human, his Iblis is the temperament and the falsehood that is within him, but it varies in degree, because this is shared by the believer and the disbeliever.
But with disbelief, the light transmutes and becomes darkness due to the dominance of the temperament of turbidity over it. And that is because he denied despite knowledge he possessed by way of guidance, so his temperament transmuted and he became an Iblis. With the believers, [it remains] mixed without transmuting, because they acknowledged, so they were safe from transmutation, and it varies among them according to merit.