In his explanation of the last two Commandments, Martin Luther first sets the stage for the giving of these laws to the ancient Israelites, then proceeds to explain how they still apply to us. It is interesting to note the difference between cultural norms of the ancient society and ours. These Commandments were necessary because women and servants were property – not people and were therefore easily taken from another. Luther points out that even if we have the right to do something, we aren’t necessarily in the right. (see Doing What is Right vs. Doing What is Our Right)
The Ninth Commandment: Thou shalt not covet thy neighbor's house
From Luther’s Small Catechism
Q. What does this mean?
A. We should fear and love God that we may not craftily seek to get our neighbor's inheritance or house, and obtain it by a show of [justice and] right, etc., but help and be of service to him in keeping it.
The Tenth Commandment: Thou shalt not covet thy neighbor's wife, nor his man-servant, nor his maid-servant, nor his cattle, nor anything that is his
From Luther’s Small Catechism
Q. What does this mean?
A. We should fear and love God that we may not estrange, force, or entice away our neighbor's wife, servants, or cattle, but urge them to stay and [diligently] do their duty.
Excerpt From Luther’s Large Catechism*
293] These two commandments are given quite exclusively to the Jews; nevertheless, in part they also concern us. For they do not interpret them as referring to unchastity or theft, because these are sufficiently forbidden above. They also thought that they had kept all those when they had done or not done the external act. Therefore God has added these two commandments in order that it be esteemed as sin and forbidden to desire or in any way to aim at getting our neighbor's wife or possessions; 294] and especially because under the Jewish government man-servants and maid-servants were not free as now to serve for wages as long as they pleased, but were their master's property with their body and all they had, as cattle and other possessions. 295] Moreover, every man had power over his wife to put her away publicly by giving her a bill of divorce, and to take another. Therefore they were in constant danger among each other that if one took a fancy to another's wife, he might allege any reason both to dismiss his own wife and to estrange the other's wife from him, that he might obtain her under pretext of right. That was not considered a sin nor disgrace with them; as little as now with hired help, when a proprietor dismisses his man-servant or maid-servant, or takes another's servants from him in any way.
296] Therefore (I say) they thus interpreted these commandments, and that rightly (although their scope reaches somewhat farther and higher), that no one think or purpose to obtain what belongs to another, such as his wife, servants, house and estate, land, meadows, cattle, even with a show of right or by a subterfuge, yet with injury to his neighbor. For above, in the Seventh Commandment, the vice is forbidden where one wrests to himself the possessions of others, or withholds them from his neighbor, which he cannot do by right. But here it is also forbidden to alienate anything from your neighbor, even though you could do so with honor in the eyes of the world, so that no one could accuse or blame you as though you had obtained it wrongfully.
307] In whatever way such things happen, we must know that God does not wish that you deprive your neighbor of anything that belongs to him, so that he suffer the loss and you gratify your avarice with it, even if you could keep it honorably before the world; for it is a secret and insidious imposition practiced under the hat, as we say, that it may not be observed. For although you go your way as if you had done no one any wrong, you have nevertheless injured your neighbor; and if it is not called stealing and cheating, yet it is called coveting your neighbor's property, that is, aiming at possession of it, enticing it away from him without his will, and being unwilling to see him enjoy what God has granted him. 308] And although the judge and every one must leave you in possession of it, yet God will not leave you therein: for He sees the deceitful heart and the malice of the world, which is sure to take an ell in addition where-ever you yield to her a finger's breadth, and at length public wrong and violence follow.
309] Therefore we allow these commandments to remain in their ordinary meaning, that it is commanded, first, that we do not desire our neighbor's damage, nor even assist, nor give occasion for it, but gladly wish and leave him what he has, and, besides, advance and preserve for him what may be for his profit and service, as we should wish to be treated. 310] Thus these commandments are especially directed against envy and miserable avarice, God wishing to remove all causes and sources whence arises everything by which we do injury to our neighbor, and therefore He expresses it in plain words: Thou shalt not covet, etc. For He would especially have the heart pure, although we shall never attain to that as long as we live here; so that this commandment will remain, like all the rest, one that will constantly accuse us and show how godly we are in the sight of God!
Large Catechism Text in the public domain. http://bookofconcord.org/lc-3-tencommandments.php