"You will certainly wear out both yourself and these people who are with you, because the task is too heavy for you. You can't do it alone.”
Jethro's advice to Moses is simple common sense, but the amazing thing is why God Himself did not suggest the same thing to Moses.
Never forget that common sense is not always the right thing to do. Common sense always says don't try to walk on water, but at the command of God we throw common sense to the wind and step out of the boat.
In this case however God apparently approved of Moses’ father-in-law’s common sense correction to what Moses was doing as judge of the people's disputes.
I believe this is one of those, “God uses the human order of authority to speak to His children” situations. I believe that Jethro was used by God to speak these words to Moses. Many years ago, when I became an adult I realized that God had used my father to speak to me when I was a child and that God still used my father to speak to me as an adult. My father would frequently express opinions or advice that ultimately proved to certainly be a Word from God!
Listen for the Voice of God at all times and in every situation. I believe God speaks much more often than any of us hear Him!