John Gill Commentary Joshua 23:6

"Therefore be ye very courageous to keep and to do all that is written in the book of the law of Moses, that ye turn not aside therefrom to the right hand or to the left;" — Joshua 23:6 (ASV)

Be you therefore very courageous to keep and to do all that is
written in the book of the law of Moses
To observe which required spiritual strength, fortitude of mind, a holy courage, a firm and fixed resolution, and particularly to destroy the Canaanites required in that book, and to abstain from all communion and fellowship with them:

that you turn not aside therefrom, [to] the right hand or the left ;
(See Gill on Joshua 1:7).