I will harden Pharaoh's heart. See the comment on Exodus 4:21. And multiply my signs and my wonders. The idea of a long series of miracles is here, for the first time, distinctly introduced. Three signs had been given (Exodus 4:3-9); one further miracle had been mentioned (Exodus 4:23).
Now a multiplication of signs and wonders is promised. Compare Exodus 3:20, and Exodus 6:6, which, however, are not so explicit as the present passage.