Satan has no truth.

John 8.44
You are of your father the devil, and the desires of your father you want to do. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he speaks a lie, he speaks from his own resources, for he is a liar and the father of it.

This verse gives a good deal of information on Satan's character. Satan has no truth in him therefore you cannot believe anything he says. He's a liar and the father of lies.

Satan is a deceiver and he's an expert in deceiving people from the truth. He has no truth in Him and therefore everything that comes out of him is a lie. He cannot speak the truth because there is no truth in him. Jesus said the word is truth. Even when he quoted Psalms 91 to Jesus, the intention was deception. It's very important to know Satan's character so you know what kind of a being he is and you won't be deceived. His ultimate objective is to steal, kill and destroy. He uses all kinds of people to display his lies to attack the truth of Gods word. For example: 'Evolution' to attack the existence of a Creator God. 'Many gods' to attack the one true God. 'Jesus was a good man' to attack the deity of Jesus. He can go to any extent in creating a lie because his only objective is to keep people away from the truth.

Friend, as you grow deeper in your understanding of Gods word, his lies will not affect your life. The only defence we have against his lies is the word of the living God. Any peice of information that is not in line with the word of God is a lie from hell irrespective of who said it. The word of God is truth. Be on your guard and gird your waist with the belt of truth. Be deception free. The word of God is first and final. Glory to God.