King David made a covenant (a binding agreement) that required the people’s loyalty. At the same time, it allowed each tribe to keep its identity and each person to keep dignity. The covenant served as a basic law for the nation. It included rules that obligated both the king and the people.
they anointed him king: Although Samuel had already anointed David earlier (1 Samuel 16:13), this public ceremony showed that the people now accepted David as their king.