What I want you to take note of are the three descriptive words used to instruct Moses as to that preparation–charge, encourage, and strengthen. I believe that this provides us as 21st century leaders with some tangible insights about how to prepare those who will and should secede us.
To “charge” in the Hebrew means to appoint, ordain or give charge. The idea is to assign one to a clear role, task or function. In other words the next leader needs to clearly know what is in front of him–what you are asking them to do. Many times it appears to me that “next leaders” are left with little clear direction or clear responsibility. New leaders need to know what and who they are to lead.
To “encourage” (ESV translation) in the Hebrew means more literally to be hard, or harsh. The connotation can include the idea of having the ability to accomplish what is intended–also implying the element of resolve. A new leader needs new leader skills. There is a sense of competency that is required. There is also a sense of determination that must be added. New leaders must have certain abilities–but all abilities can be enhanced and improved. And any leader who secedes another will need resolve to follow God and cut their own path. The old leader “encourages” the new leader through improving the new leader’s abilities and infusing a sense of resolve.
To “strengthen” in the Hebrew means to marshal force or to be courageous. If “encouraging” was primarily about improving abilities then “strengthening” is primarily about attitude. It carries the idea of focus. No leader is worth his salt without focus. As I have said before, the key to complexity is not simplicity but focus. Old leaders need to help new leaders focus–to marshal all that God has given them for a God given task. Seceding leaders can easily become distracted–the outgoing leader must help them rightly focus on the task ahead.
Here is how Moses was to aid Joshua in taking over as leader of the people of Israel: make the task as clear as possible, help him improve his God given abilities with a sense of resolve, and help him step out in courageous faith with an unwavering focus.