זוהר שמות — דף נג ע”ב

The Patriarchs — Abraham, Isaac and Jacob — form the chariot (merkavah) with King David, and through their merit redemption is always readied for Israel. The divine hand is no fewer than five fingers, and when it includes five additional ones it is called "great" — an allusion to the ten sefirot. During the first five plagues Pharaoh hardened his own heart, then afterward the Holy One Himself hardened it. Israel saw the Egyptians dead upon the seashore, which occurred when the lower world (Malkhut) was aroused to perform miracles and mighty deeds.