i.e. To gain thee authority and reputation among them, as the person whom I have set in Moses's stead, and by whom I will conduct them to the possession of the promised land.
Related Commentaries of Joshua 3:7
Joshua 3:7
7 And the LORD said unto Joshua, This day will I begin to magnify thee in the sight of all Israel, that they may know that, as I was with Moses, so I will be with thee.