And, how do you know that?
Because I know what the Bible says about him...
"You are from your father the Devil, and you wish to do the desires of your father. That one was a murderer when he began, and he did not stand fast in the truth, because truth is not in him. When he speaks the lie, he speaks according to his own disposition, because he is a liar and the father of the lie." John 8:44
"The one who practices sin originates with the Devil, because the Devil has been sinning from the beginning. For this purpose the Son of God was made manifest, to break up the works of the Devil." 1 John 3:8
"Therefore, since the “young children” are sharers of blood and flesh, he also similarly shared in the same things, so that through his death he might bring to nothing the one having the means to cause death, that is, the Devil," Hebrews 2:14