Or HaChaim on Exodus 7:14/אור החיים על שמות ז׳:י״ד

1 ויאמר ה׳ אל משה כבד לב פרעה, G'd said to Moses: "Pharaoh's heart is stubborn, etc." What did G'd tell Moses here that he did not already know? Perhaps Pharaoh had not refused the request to let the Israelites go in so many words, but had merely remained silent after watching Aaron's demonstration. G'd informed Moses that the meaning of this silence was that Pharaoh refused to release the Israelites and did not even think it necessary to say so.