After David sinned with Bethsheba the prophet Nathan was sent to him by God, in order that his sin might be exposed unto him. He did so by telling him the parable which we read in 2 Samuel 12:1-6.
Later Nathan tells David, that he (David) is the rich man from the parable. That's how we conclude that the poor man is Uriah the Hittite and the lamb is his wife Bethsheba.
Now my question is whether someone has thought on who the traveler / guest, referred to in the parable, is?
2 Samuel 12:4 (ESV)
Now there came a traveler to the rich man, and he was unwilling to take one of his own flock or herd to prepare for the guest who had come to him, but he took the poor man's lamb and prepared it for the man who had come to him.”