1 Chronicles 24:6
And Shemaiah the son of Nethaneel the scribe, one of the Levites, wrote them before the king, and the princes, and Zadok the priest, and Ahimelech the son of Abiathar, and before the chief of the fathers of the priests and Levites: one principal household being taken for Eleazar, and one taken for Ithamar.
The verse is part of David's careful assigning of special duties to the men best fitted for them, a system he studied out and brought to perfection for Solomon's reign to govern the priests and Levites, the civil officers, and the army. Within that larger organization the priests were divided into twenty-four courses. Of that division a full and accurate record was made, with the writing done in the presence of the king and leaders, and each course was thoroughly organized under its own chief. Under this arrangement each course was to come to Jerusalem twice a year to attend for one week to the ministry of the sanctuary.