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 ) .