John Gill Commentary 2 Chronicles 35:4

"And prepare yourselves after your fathers` houses by your courses, according to the writing of David king of Israel, and according to the writing of Solomon his son." — 2 Chronicles 35:4 (ASV)

And prepare yourselves To do their work in this service of the sanctuary, the passover; that they be ready to do it, and diligent in it, and perform it according to the law of God:

by the houses of your fathers, after your courses ; such of them whose turn in course it was to officiate:

according to the writing of David king of Israel, and according to the writing of Solomon his son ; who had given in writing directions in what manner their courses should be observed, see (1 Chronicles 23:1–24:31) .