Exodus 9:14

For I will at this time send all My plagues upon thine heart and upon thy servants and upon thy people, that thou mayest know that there is none like Me in all the earth. The threat in this case is more fearful, and seems to include all the remaining plagues, which were to be directed against the obdurate heart of the king, but were also to affect his servants and all his people, since they all consented to the sins of Pharaoh. The final purpose was to establish the fact that the Lord God of the Hebrews was the one true God in all the earth.