The Fifth to the Tenth Commandments all teach us to guard against harming our neighbour in any way (1 Thess 4:3-5; 1 Cor 6:9-11). They are admirably arranged. First, they deal with our neighbours’ person. Then they proceed to the person nearest and dearest to him, namely his wife, (spouse)who is one flesh and blood with him. In no possession of his can we inflict a greater injury upon him. Therefore, it is explicitly forbidden here to dishonour his wife. (Concordia 393:200).
In as much as there is a shameful mess and cesspool of all kinds of vice and lewdness among us, (Matt 5:28; 1 John 2:16) this commandment applies to every form of unchastity; however, it is called. Not only is the external act forbidden, but also every kind of cause, motive and means. Your heart, your lips, and your whole body are to be chaste and to afford no occasion, aid, or encouragement to unchastity (393:202)
God honours and glorifies the married life, (Gen 2:24, Mark 10:6-9, 1 Cor 7:8,9, Heb 13:4) sanctioning and protecting it by his commandment…He establishes it as the first of all institutions, and he created man and woman differently (as is evident) not for lewdness but to be true to each other, be fruitful, beget children and support and bring them up to the glory of God (3030:206-207)
It is not an estate to be placed on a level with others; it precedes and surpasses them all (393:209).