David's fall from grace involved some very heinous conduct. While Saul seemed to struggle with obedience his whole life, David generally did what God required. What is more, he united Israel and then started expanding its borders. Nonetheless, like men of power that we all have read about, it appears his libido got the best of him when "[o]ne evening [he] got up from his bed and walked around on the roof of the palace. From the roof he saw a woman bathing. The woman was very beautiful," and David had to have her. 2 Sam. 11:2. So, not only does he sleep with another man's wife, he sends that man to die in battle so he can have the woman to himself. Then, his prophet Nathan tells this story:
The LORD sent Nathan to David. When he came to him, he said, "There were two men in a certain town, one rich and the other poor. The rich man had a very large number of sheep and cattle, but the poor man had nothing except one little ewe lamb he had bought. He raised it, and it grew up with him and his children. It shared his food, drank from his cup and even slept in his arms. It was like a daughter to him.Of course, it turns out that *snap* the man is David! I didn't remember the little parable. Here is the full story.
"Now a traveler came to the rich man, but the rich man refrained from taking one of his own sheep or cattle to prepare a meal for the traveler who had come to him. Instead, he took the ewe lamb that belonged to the poor man and prepared it for the one who had come to him."
David burned with anger against the man and said to Nathan, "As surely as the LORD lives, the man who did this deserves to die! He must pay for that lamb four times over, because he did such a thing and had no pity."