Read 2 Samuel 11.
For the most part, everything has been good for David up to this point. With each chapter we hear about God's promises to David, David's victories, and his military prowess. But then the first verse of chapter 11 hints at an upcoming problem.
"In the spring, at the time when kings go off to war, David sent Joab out with the king's men and the whole Israelite army."
David wasn't where he was supposed to be. And the story only gets worse. He sees Bathsheba, gets her brought to the palace, and he sleeps with her. Once she sends notice of her pregnancy, David panics. What will people think? How will this make me look? How can I make sure no one finds out? In haste, David brings Uriah home from battle with the hope that he will sleep with Bathsheba. When he doesn't, David's desperation gets the best of him. It's bad enough that he has committed adultery, but now he commits murder when he sends notice to make sure that Uriah dies in battle.
It's hard to believe but this is David, the man after God's own heart, doing these things. And it marks the beginning of his downfall. But perhaps the most ringing message of hope from this passage is that this isn't the end. David is still in Jesus' genealogy. David is still Israel's king. He still has a special relationship with God. David messed up, but God doesn't let him go.
And that's a message that is true for all of us. We all sin and fall short of the glory of God (as Paul tells us in Romans 3:23) but that isn't the end of the story. We know that because Christmas is coming, and we celebrate that God came to us in the flesh. Jesus entered into our sin, our brokenness, our suffering, giving us a way out.
And so we have hope. David's story doesn't end with sin, and neither do our own stories. Rather our sin points us to Christmas, to Jesus, to the cross, and we have hope.