They performed the service of their God and the service of purification, along with the singers and gatekeepers, as David and his son Solomon had prescribed.
KJV
And both the singers and the porters kept the ward of their God, and the ward of the purification, according to the commandment of David, [and] of Solomon his son.
ASV
And they kept the charge of their God, and the charge of the purification, and so did the singers and the porters, according to the commandment of David, and of Solomon his son.