Joshua 1:16-17 And they answered Joshua, saying, All that thou commandest us we will do, and whithersoever thou sendest us, we will go. According as we hearkened unto Moses in all things, so will we hearken unto thee: only the Lord thy God be with thee, as he was with Moses.
Reuben, Gad, and the half-tribe of Manasseh were given land to occupy on the east side of Jordan. The proviso, however, was that they would fight with their fellow Israelites for the west side. Then, after the Conquest, they would return to their designated land. This they agreed to do: they would do what Joshua said and go where he sent them.
They listened to Moses, and now they would listen to his chosen successor. This was an important transition of leadership. It was important to submit to one chosen prophet and do and go as he said. The Lord chooses and sends various leaders in the church today, apostles, prophets, evangelists, pastors, teachers, etc. Our response is to hearken, do, and go. This chosen servant is called and sent. Jesus is speaking; listen to Him. And so the 2 1/2 tribes did respond, and were blessed.
The only request the people make to their leader is that God be with him, meaning, you make sure you are listening to the Lord. You spend your time with the Lord, in His Word, hearing the pure truth, and then we can respond confidently to your leadership. This is what NT believers rightfully expect from their preachers, teachers, and leaders: “We will follow you if you are following the Lord.” Lay members may demand that pastors rightly distinguish Law and Gospel. Then they respond by doing and going, by believing and being saved.