Why were the heads of the people of Israel to be brought together before the exodus?

Les explains that after God revealed Himself as the I Am, the God of Abraham, Isaac, and Jacob, and told Moses to say that name to the children of Israel, they were to bring all the heads of the people together so that He could announce to them that the time of their deliverance was at hand. God then told Moses that He was sure the king of Egypt would not let them go, not by a mighty hand, but God would stretch out His hand and smite Egypt with all His wonders, and after the plagues the king would let them go. Les also clarifies that the women were to ask, not borrow, from the Egyptians, and the Egyptians would unload their wealth on the Israelites as they left.