As long as Moses held up his hands, the Israelites were winning, but whenever he lowered his hands, the Amalekites were winning. When Moses’ hands grew tired, they took a stone and put it under him and he sat on it. Aaron and Hur held his hands up—one on one side, one on the other—so that his hands remained steady till sunset. So Joshua overcame the Amalekite army with the sword.
Exodus 17:11-13 New International Version (NIV)
The next day Moses took his seat to serve as judge for the people, and they stood around him from morning till evening. When his father-in-law saw all that Moses was doing for the people, he said, “What is this you are doing for the people? Why do you alone sit as judge, while all these people stand around you from morning till evening?”
Exodus 18:13-14 (NIV)
Listen now to me and I will give you some advice, and may God be with you. You must be the people’s representative before God and bring their disputes to him. Teach them his decrees and instructions, and show them the way they are to live and how they are to behave. But select capable men from all the people—men who fear God, trustworthy men who hate dishonest gain—and appoint them as officials over thousands, hundreds, fifties and tens. Have them serve as judges for the people at all times, but have them bring every difficult case to you; the simple cases they can decide themselves. That will make your load lighter, because they will share it with you. If you do this and God so commands, you will be able to stand the strain, and all these people will go home satisfied.”
Exodus 18:19-23 (NIV)