What does 2 Samuel 12:4 mean?

One day, a guest showed up at the rich man’s house. Instead of taking a sheep or cow from his own herd to feed the visitor, the rich man took the poor man’s only lamb and cooked it for his guest. 2 Samuel 12:4 - Modern Text Bible

(The rich man’s action is shockingly selfish and cruel, especially given his resources. Nathan’s story is meant to provoke outrage at this injustice.)