The people of Israel once had the opportunity to cross over the river Jordan to lay claim to the land that God had promised them. Because of their disbelief, they had been consigned to 40 years of wandering. Now, they again have the chance to cross over and as they prepare to do so, God calls them to be strong and courageous.
The land was meant to be their rest, a place where they could be God's people, to grow in the knowledge of Him. That was the true promise.
It would require being steadfast in a trust of the One who had made the promise. It would require courage in the face of adversity.
We as believers today are called to be God's people, inhabitants of His Kingdom. God will, we trust, ultimately bring s the peace of God which passes all understanding, for we have sufficient faith to prove ourselves as His people and therefore, the Lord will surely bring us in. But it will take a great deal of marching for what may seem, at the present, very small amount of progress.