Derech Eretz Kadma L'Torah - To Be a Mensch
In its most basic sense, this principle teaches that it is impossible to be rude, arrogant, rough and unpleasant while remaining a devoted servant of God. It is a contradiction. So, Moshe went and returned to Jethro...and said to him, "Let me now go back to my brethren...And Jethro said, 'Go in peace.' It is as if Moshe held up his hands to God and declared, "Hold on while I see if it's all right to follow your command." And if Jethro said, No? What then?