Falsehood is from the Evil One
In the Scriptures, it is written that falsehood is from the evil one and that He is the “Father of lies” (John 8:44), while God is truth, for He Himself says, “I am the way, the truth, and the life.” (John 14:6). Thus you see from Whom we estranged ourselves and to whom we are united by a lie. So then, if we really want to be saved, we must love truth with our whole hearts and guard ourselves from all falsehood. There are three different types of lies: in thought, in word, and in life itself. A man lies in thought when he accepts as true his own imaginations, that is his vain despite of his neighbor. Such a one, when he sees that someone is conversing with his neighbor, makes his own estimation and says, “They are talking about me.” If someone says a word, he considers that it was said to grieve him. Never believe your own guesses and interpretations, for a crooked measurement makes even the straight to be crooked. Human opinion is false and harms those who are given to it. The one who sins in word is one who, for example, when out of despondency he has not gotten up for the service, does not say, “Forgive me, I was too lazy to get up,” but says, “I had a fever, I had too much work, I hadn’t the strength to get up, I was sick,” and says ten false statements, rather than make a single prostration and be humbled. And if he should be rebuke in such a situation, he changes his words and argues, in order not to be rebuked. One who lies by his life is one who, if he is defiled, pretends to be chaste, or if he is avaricious, praises almsgiving, or if he is proud praises humility. Thus, in order to escape falsehood and be delivered from the part of the evil one, let us strive to appropriate truth, in order to have union with God. (St. Abba Dorotheos, Soul-profiting Teachings.
St. Dorotheus of Gaza.