Why did the Jews from Moses onward need signs to be convinced of what God was saying and doing?
From Moses onward, the Jews had to have signs to be convinced of what God was saying and doing. This pattern ran through their history. Scripture connects it to God's chosen wisdom: He uses the foolish and weak to confound the wise and mighty, as with Moses, whom God could not use while he was mighty in himself.
Les teaches that the Jews, beginning with Moses and continuing all the way up through their history, had to have signs in order to be convinced of what God was saying and what He was doing. Before looking at the sign aspect, Les points to 1 Corinthians chapter 1, where Paul lays out the wisdom that can come only from God and not from men. Paul writes that not many wise men after the flesh, not many mighty, not many noble, are called. Instead, God has chosen the foolish things of the world to confound the wise, and the weak things of the world to confound the things which are mighty. Les puts this in perspective with Moses: when Moses was mighty, when he had power and clout, God could not use him. Moses went out in the energy of the flesh and thought he could deliver the children of Israel. God therefore had to put Moses on the backside of the desert for 40 years to prepare him as an instrument God could use. This illustrates God's chosen way of confounding human wisdom and strength, and it fits the Jews' history of requiring signs to be convinced of God's speaking and working.