Joshua 5

To Joshua, the Lord provided this counsel and promise -

"Be strong and of a good courage: for unto this people shalt thou divide for an inheritance the land, which I sware unto their fathers to give them.
7 Only be thou strong and very courageous, that thou mayest observe to do according to all the law, which Moses my servant commanded thee: turn not from it to the right hand or to the left, that thou mayest prosper whithersoever thou goest.
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." (Old Testament | Joshua 1:6 - 8)

And then he added this strong promise -

"...Be strong and of a good courage; be not afraid, neither be thou dismayed: for the LORD thy God is with thee whithersoever thou goest." (Old Testament | Joshua 1:9)

As Joshua is about to embark on his mission to acquire the promised land, we read that -

"...it came to pass, when Joshua was by Jericho, that he lifted up his eyes and looked, and, behold, there stood a man over against him with his sword drawn in his hand: and Joshua went unto him, and said unto him, Art thou for us, or for our adversaries?" (Old Testament | Joshua 5:13)

And in answer, the soldier confessed -

"...Nay; but as captain of the host of the LORD am I now come..." (Old Testament | Joshua 5:14)

The Lord had promised that if Joshua was strong and of good courage, the Lord would be with him. In this case, it became apparent that the armies of the Lord were with Joshua.