Catechesis: Sixth Commandment

Therefore, this commandment is directed against all kinds of unchastity, whatever it may be called. Not only is the outward act of adultery forbidden, but also every kind of cause, motive, and means of adultery. Then the heart, the lips, and the whole body may be chaste and offer no opportunity, help, or persuasion toward inchastity.—LC I:202, 203