Deuteronomy 31:7
And Moses called unto Joshua, and said unto him in the sight of all Israel, Be strong and of a good courage: for thou must go with this people unto the land which the LORD hath sworn unto their fathers to give them; and thou shalt cause them to inherit it.
Moses called Joshua before the eyes of all Israel to publicly commission him to lead the people after himself into the land promised to their fathers and to cause them to inherit it. As the older and experienced leader, Moses was to strengthen and encourage the younger Joshua so that he could carry forward God's work with courage. That relationship stands as the pattern for experienced workers toward younger workers, and experienced workers who refuse to support the work God is advancing fail to fill the place they might have filled and become a hindrance rather than a blessing to it.