Next to our own person and our spouse, our temporal property is dearest to us. This too, God wants to have protected. He has forbidden us to rob or pilfer the possessions of our neighbour…This includes taking advantage of our neighbour in any sort of dealing that results in loss to him…A person steals not only when he robs a man’s stronghold or his pocket, but also when he takes advantage of his neighbour at the market, in a grocery shop, butcher stall, wine and beer cellar, workshop, and in short, wherever business is transacted and money is exchanged for goods or labour. (Concordia: 395:223-224)
Suppose, for example, that a man-servant or maid-servant (worker), is unfaithful in his or her domestic duty and does damage or permits damage to happen when it could have been avoided. Or suppose that through laziness, carelessness, or malice a servant wastes and neglects things to the vexation and annoyance of his master or mistress. (Ephesians 4:28; 2 Thessalonians 3:6-8) When this is done deliberately – for I am not speaking of what happens inadvertently or unintentionally – a servant can cheat his employer out of thirty or forty gulden or more a year. If a thief had taken such sums he would be strangled with a noose, but the servant may even become defiant and insolent and dare anyone to call him a thief! (395:225)
Let everyone know, then that it is his duty, at the risk of God’s displeasure, not to harm his neighbour, take advantage of him, or defraud him by any faithless or underhanded business transaction. (Philippians 2:4; Exodus 23:4-5; Genesis 13:8-12) More than that, he is under obligation faithfully to protect his neighbour’s property and further his interests, especially when he takes renumeration for such services (396;233)
Excerpts from Large Catechism; Seventh Commandment.