This book of the law i.e. the five books referred to as one throughout the Old Testament. See App-47.
mouth. Put by Figure of speech Metonymy (of Cause), for what is spoken by it (App-6), i.e. Joshua is to continually speak of it,
meditate. talk to thyself. Compare Psalms 1:2. audible musing.
way. Some codices with one early printed edition, read "ways".