Shall not depart out of thy mouth, i.e. thou shalt constantly read it, and upon occasion discourse of it, and the sentence which shall come out of thy mouth shall in all things be given according to this rule. Meditate therein, i.e. diligently study, and frequently and upon all occasions consider what is God's will and thy duty. The greatness of thy place and employments shall not hinder thee from this work, because this is the only rule of all thy private actions and public administrations. According to all that is written therein; whereby he teacheth him that it is his duty to see with his own eyes, and to understand the mind and law of God himself, and not blindly to follow what any other should advise him to.
Related Commentaries of Joshua 1:8
Joshua 1:8
8 This book of the law shall not depart out of thy mouth; but thou shalt meditate therein day and night, that thou mayest observe to do according to all that is written therein: for then thou shalt make thy way prosperous, and then thou shalt have good success.