Catechism of the Catholic Church §2504 — excerpt
"You shall not bear false witness against your neighbor" (Ex 20:16). Christ's disciples have "put on the new man, created after the likeness of God in true righteousness and holiness" (Eph 4:24).
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.