Free will derives from the "Holy Spirit" nature of God. This "nature" of God first revealed itself to Moses. You know, the guy whose mom gave him up at birth to the Pharaoh's daughters bathing in the river, fought off the Egyptian guards, the attackers at the well, got in the Pharaohs face and demanded "let my people go", and then proceeded to ride out 7 plagues, the guy who crossed the red sea. Every inch of that story is balls to the wall choices. Nobody could read that thinking that this guy was just a pleb of circumstance. Also, the commandments Moses brought down from the mount, why have commandments if people didn't have choices. Even the symbols of the Holy Spirit, like a dove that flies in unknown direction, or a bush that burns but is not consumed represents the passion and freedom so often associated with free will. The Jews were at a time in there history where they were questioning if they were meant to be slaves, were destined by circumstance, or there was more. The answer to that was the Holy Spirit, a nature of God which directly implied free will.