At the end of 1st Kings 1, David ensured Solomon’s succession to the throne and strictly speaking, David is no longer the king because there can only be one king on the throne at a time. Here, David charges Solomon with several pieces of advice to try to ensure Solomon’s success and long reign.
After the prophet Natan (Nathan) confronted David over his adultery with bat-Sheba (Bathsheba) and murder of her husband, Uriah, David expresses true repentance — revealed in Psalm 51 — and is granted mercy.
This is the second time Nathan had to come to David with a word from the Lord, at least the second time recorded in Scripture. But this time David spoke the prophetic word upon himself.
David committed a series of sins that started out minor and culminated in the most egregious of sins of adultery and murder. This tragedy sets up a series of later tragedies that nearly take David off the throne permanently but they also harken back to the story of Adam and Eve and their fall from grace.