What did the Jews from Moses onward require to be convinced of what God was saying and doing?
From Moses onward, the Jews required signs to be convinced of what God was saying and doing. Their long history demonstrates this repeated need: they did not simply take God at His word but sought confirming signs as evidence of His speaking and activity.
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 goes to 1 Corinthians chapter 1, where Paul lays out the wisdom that can come only from God and not from men. There Paul writes that not many wise men after the flesh, not many mighty, not many noble, are called; instead God chose the foolish things of the world to confound the wise and the weak things to confound the things which are mighty. Les connects this directly to Moses: when Moses was mighty, had power, and had clout, God could not use him. Moses went out in the energy of the flesh and thought he could deliver the children of Israel, so God put him on the backside of the desert for 40 years to prepare him as an instrument God could use.