זוהר שמות — דף לא ע”ב

The ways of the Torah are ways of pleasantness opened from the Patriarchs into the great sea. This pleasantness is the World to Come which illuminates all the lights. At the end of Shabbat, one must arouse supernal joy to be protected from the punishment of the wicked. Three types of deaths struck the animals of Egypt: plague, hail, and death of the firstborn. The plague was called the Hand of the Divine with five fingers corresponding to five species of animals. Since the Egyptians did not repent, the plague turned into hail.