'Liar' in the Bible

The father whose sons you are is the Devil; and you desire to do what gives him pleasure. *He* was a murderer from the beginning, and does not stand firm in the truth--for there is no truth in him. Whenever he utters his lie, he utters it out of his own store; for he is a liar, and the father of lies.

You do not know Him, but I know Him perfectly; and were I to deny my knowledge of Him, I should resemble you, and be a liar. On the contrary I do know Him, and I obey His commands.