2 Chronicles 35:15

The singers, the sons of Asaph, were in their place, according to the commandment of David, Asaph, Heman, and Jeduthun the king’s seer; and the gatekeepers were at every gate. They didn’t need to depart from their service, because their brothers the Levites prepared for them.

And the singers the sons of Asaph were in their place, according to the commandment of David, and Asaph, and Heman, and Jeduthun the king’s seer; and the porters waited at every gate; they might not depart from their service; for their brethren the Levites prepared for them.