God divided the ten punishments decreed for Egypt into four parts, three of the plagues He committed to Aaron, three to Moses, one to the two brothers together, and three He reserved for Himself. Aaron was charged with those, that proceeded from the earth and the water, the elements that are composed of more or less solid parts, from which are fashioned all the corporeal, distinctive entities, while the three entrusted to Moses were those that proceeded from the air and the fire, the elements that are most prolific of life.