2 Chronicles 35:15 YLT

[15] And the singers, sons of Asaph, [are] on their station, according to the command of David, and Asaph, and Heman, and Jeduthun seer of the king, and the gate keepers [are] at gate and gate; it is not for them to turn aside from off their service, for their brethren the Levites have prepared for them.