Rab Judah said in the name of Rab: 'What is signified by the verse, And they oppress a man and his house, even a man and his heritage? A certain man once conceived a desire for the wife of his master, he being a carpenter's apprentice. Once his master wanted to borrow some money from him. He said to him: Send your wife to me and I will lend her the money. So he sent his wife to him, and she stayed three days with him. He then went to him before her. Where is my wife whom I sent to you? he asked. He replied: I sent her away at once, but I heard that the youngsters played with her on the road. What shall I do? he said. If you listen to my advice, he replied, divorce her. But, he said, she has a large marriage settlement. Said the other: I will lend you money to give her for her Kethubah. So he went and divorced her and the other went and married her. When the time for payment arrived and he was not able to pay him, he said: Come and work off your debt with me. So they used to sit and eat and drink while he waited on them, and tears used to fall from his eyes and drop into their cups. From that hour the doom was sealed;On Erev Tish'a B'av I learned this piece of Gemara in a shiur. This was put forward as an example of Naval B'reshut HaTorah - loosely, someone who violates the spirit of the law, without violating the letter of the law.
(Masechet Gittin 58a) (english translation)
A couple of days ago it occured to me that this is a really bad example of violating only the spirit of the law. Why? Because the whole situation derives from him transgressing one of the Ten Commandments לא תחמד - thou shalt not covet thy neighbor's wife. He violated the spirit as well as the letter of the law. This seems to be to be more a lesson of how horribly one can stray when a basic law is overlooked and transgressed without thought.