David knew that the Lord had made his position as king secure. He knew that the Lord had made him king over the whole nation of Israel. He knew that the Lord had greatly honored his kingdom. The Lord had done it because the Israelites were his people.
The Lord has given me many sons. From all of them he has chosen my son Solomon. He wants Solomon to sit on the throne of the Lord’s kingdom. He wants him to rule over Israel.
You love your wife. So enjoy life with her. Do it all the days of this meaningless life God has given you on earth. That’s what he made you for. That’s what you get for all your hard work on earth.
You ask, “Why?” It’s because the Lord is holding you responsible. He watches how you treat the wife you married when you were young. You have been unfaithful to her. You did it even though she’s your partner. You promised to stay married to her. And the Lord was a witness to it.