A Liar and a Murderer
In John 8:44, Jesus says, "[The devil] was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he lies, he speaks out of his own character, for he is a liar and the father of lies."
There are two characteristics of Satan that Jesus highlights for us here, to teach us. The first is that the devil is a liar. God's word is truth, and it guides us as a lamp in the darkness showing us our sinfulness and pointing us to Jesus our Savior. The devil seeks to draw you away from the truth of God's word by lying to you, by trying to convince you that God's word is not true. The devil is the chief liar, the source of all lies, the "father of lies" Jesus calls him. His lies are subtle and sneaky. He lies by telling half-truths, by twisting God's word, or by quoting it out of context, just as he did in the garden of Eden with Adam and Eve and in the wilderness with Jesus.
And why all this lying? In order to serve Satan's second prominent trait; he is a murderer. He seeks to murder you. Satan lies to you to draw you away from God, so that you would serve him, and dwell with him in the everlasting death of hell. That's his goal. He wants to destroy and pervert what God has created good. The highest good of God's creation is human beings, you and me. The devil's eternal destiny is hell, and he wants to pull as many people down with him as possible. He lies in order to murder.
But Satan is defeated. The war between Satan and the Lord, begun in Eden, continued as Jesus was tempted in the wilderness, was finished at the cross and Jesus' empty tomb. Satan lost. Though the war is over, and Satan's final destination is assured, he still wages battles against humanity, especially against God's people. He continues to lie. He wants you to conform to the culture instead of God's word. He wants to confuse good and evil, right and wrong in your mind. He wants you to doubt the promise of your baptism, the certainty that your sins are forgiven, and the continued mercy of God in your life. He wants you to do something, anything, other than being in church on Sunday morning where God's word, and Christ's body and blood strengthen your faith. Don't listen to him. Instead, trust your Lord who has called you out of Satan's darkness into His marvelous light.