A pattern emerges as the fourth plague is released by God. We see a symmetrical, unfolding scheme. The first nine plagues are a series of three plagues each. The first is announced by Moses at the Nile, the second by Moses at the palace and the third without warning. The final one is the climax of all that came before, “I am the Lord, and I will punish the gods of Egypt” (Exodus 12:12b). As the swarms of flies are released into Egypt, God makes a distinction between his people and the Egyptians.