What does 1 Kings 1:28 mean?

Bathsheba was the wife of Uriah, one of David's mighty warriors (2 Samuel 23:39). While Uriah was at war, David saw her ritually bathing. He sent servants to bring her to him, and he slept with her. She became pregnant. David recalled Uriah from the battlefield and tried to entice him to sleep with his wife so he would think the baby was his. Uriah refused, and David arranged for him to be killed in battle (2 Samuel 11:1–21).

Nathan the prophet confronted David over this sin. He predicted that the child would die. David took Bathsheba as his wife. She gave birth. The boy died (2 Samuel 11:27; 12:18). David saw how much he had hurt Bathsheba. He did the culturally appropriate thing and gave her a son, Solomon (2 Samuel 12:24–25). In fact, he gave her four sons, more than any of his other wives (1 Chronicles 3:5). When God told David that Solomon would be his heir (1 Chronicles 28:6), he told Bathsheba.

While this is clearly David's intent, and many know about it, he hasn't made it official. He certainly had not convinced his son Adonijah that he would not be king. There is no official public declaration that Solomon is the heir.

And so, while David lies old and frail in his bedchambers, Adonijah is just south of the city, throwing himself a coronation party. Nathan enlisted the help of Bathsheba to warn David and compel him to act. If he doesn't, Solomon won't be king, and Adonijah will likely kill Bathsheba, Solomon, Nathan, and David's loyal officials (1 Kings 1:1–27).

The scheme works. David calls Bathsheba back to his rooms to swear to her, once again, that Solomon will be king. In fact, her son will sit on the throne this very day (1 Kings 1:29–30).