"You shall not commit adultery."
What does this mean? We should fear and love God so that we lead a sexually pure and decent life in what we say and do, and husband and wife love and honor each other.
Setting aside the First Commandment, there is something unique about the Sixth Commandment's What does this mean? That is, it leaves out what we mustn't do. Every other What does this mean? (with the special exception of the First Commandment) begins by saying what we should not do - and then what we should.
But under the Sixth Commandment, which deals with sexual purity and marriage, Luther omits any reference to sexual sins, perhaps in the belief that it would be shameful even to mention them (Eph. 5:3, 12). How refreshing in an age when we have forgotten how to blush (Jer. 6:15; 8:12)!
Luther focuses on the beautiful things: chastity, modesty, and a loving marriage. This is what we should do too.
For a list of sins against the Sixth Commandment, one may consult the Explanation. But to discover and meditate on the blessed essence of this commandment, and apply it to one's life, nothing more is needed than this:
We should fear and love God so that we lead a sexually pure and decent life in what we say and do, and husband and wife love and honor each other.