Verses 1-19 focus on the priests, while verses 20-31 list a different group of Levites that conflicts with 23:6-24. This section about the priests explains the division of the clergy into 24 classes, which the Chronicler attributes to David. However, this system developed after the exile, and the Chronicler seeks to justify the separate classes of priests—those of Abiathar and those of Zadok—by referencing David.