“The divisions of the descendents of Aaron were these. The sons of Aaron were Nadab, Abihu, Eleazar, and Ithamar. But Nadab and Abihu died before their father. They had no sons. Thus Eleazar and Ithamar became the priests. Along with Zadok of the sons of Eleazar, and Ahimelech of the sons of Ithamar, King David organized them according to the appointed duties in their service. Since more chief men were found among the sons of Eleazar than among the sons of Ithamar, they organized them under sixteen heads of ancestral houses of the sons of Eleazar, and eight of the sons of Ithamar. They organized them by lot, all alike, for there were officers of the sanctuary and officers of God among both the sons of Eleazar and the sons of Ithamar. The scribe Shemaiah son of Nethanel, a Levite, recorded them in the presence of the king, the officers, Zadok the priest, and Ahimelech son of Abiathar, and the heads of the ancestral houses of the priests and of the Levites. One ancestral house was chosen for Eleazar and one chosen for Ithamar.”
The priests seem to be sons of Aaron. They are listed separately from the Levites. This beginning is loosely based on Numbers, chapter 3. Aaron had 4 sons. 2 died, Nadab and Abihu, without children when they presented unholy fire before Yahweh as mentioned in Leviticus, chapter 10. However, the other 2, Eleazar and Ithamar, served as priests with their father Aaron. This biblical chronicler makes Eleazar more important than Ithamar, when the other writings have Ithamar as the high priest. They were organized by lot. This seems to be the common way that things happened. The father of Zadok was made high priest by Saul after the extermination of the family of Ahimelech in 2 Samuel, chapter 8. This Zadok was the trusted priest friend of King David, who helped to put Solomon on the throne. This Ahimelech was the grandson of the slain Ahimelech. Although there are over 18 people with the name of Shemaiah, many of them Levites, this son of Nethanel was the scribe and recorder for David.