Here is a condensed version of Fr. Thomas Hopko’s writing on Honesty from his book, The Orthodox Faith which you can find online at https://www.oca.org/orthodoxy/the-orthodox-faith
The wise man who has knowledge lives according to the truth through a totally honest life. Honesty means, first of all, to speak the truth and never to “bear false witness” (Ex 20.16).
This basic scriptural teaching is also that of the apostles.
For we pray to God that you may not do what is wrong . . . but that you may do what is honest . . . for we cannot do anything against the truth, but only for the truth (2 Cor 13.7–8).
Honesty also means to act truly and openly, without pretense, or the presentation of a false image of oneself. It means, in a word, not to be a hypocrite.
Above all things, Christ the Lord hated and condemned hypocrisy, lying, and deceit. He accused the devil himself, first and foremost, of being a deceiver and liar, pretending to be other than he is, presenting himself and his teaching as totally other than the falsehood and wickedness that they actually are (cf. Jn 8.44–47). This is the way of all the false prophets, and of the antichrist himself.
For many deceivers have gone out into the world, men who will not acknowledge the coming of Jesus Christ in the flesh; such a one is the deceiver and the antichrist (2 Jn 7).
In His fierce condemnation of the evil of the scribes, Pharisees, and lawyers, Christ was most violent against their hypocrisy. Of all the evils of men, the most vile in the sight of the Lord is undoubtedly hypocrisy.
The spiritual person is not a hypocrite. He shows himself honestly for what he is, and does not pretend to be what he is not. He reveals himself to all exactly as he actually is. He does not say or do anything that would lead people to have a false impression of him or of anyone or anything. He is utterly honest and pure in all that he thinks, says and does, knowing that God sees all and judges with righteousness all those who “walk-in integrity” (cf. Ps 26.1, 11).