The priestly divisions or sacerdotal courses (Hebrew: mishmar (מִשְׁמָר)) are ritual work groups in Judaism originally formed during the reign of King David in the 10th century BCE as documented in the biblical passage of 1 Chronicles 24. These priests were all descendants of Aaron, known also as Aaronites. Aaron had four sons: Nadab, Abihu, Eleazar and Ithamar. However, Nadab and Abihu died before Aaron and only Eleazar and Ithamar had sons. One priest, Zadok, from Eleazar's descendants and another priest, Ahimelech, from Ithamar's descendants, were designated by King David to help create the various priestly work groups. Sixteen of Eleazar's descendants were selected to head priestly orders while only eight of Ithamar's descendants were so chosen. The passage states that this was done be