Adam Clarke on Joshua 1:7

Only be thou strong, and very courageous - Ισχυε ουν, και ανδριζου σφοδρα. - Sept. Be strong therefore, and play the man to the uttermost. Though God had promised him that no man should be able to stand before him, yet it was on condition that he should use all his military skill, and avail himself to the uttermost of all the means, natural and providential, which God should place within his reach. God will not have them who refuse to help themselves.