I judge … and I do make them know the statutes of God. As the Israelites were, up to this time, without any code of written laws, Moses took the opportunity furnished by such cases as came before him, to lay down principles of law, and enjoin them upon the people; thus making them to know the statutes of God and his eternal unwritten laws.
Such a practice would not have been necessary after the giving of the law on Mount Sinai; and its existence at the time of Jethro's visit helps to fix that visit as occurring before the giving of the law.