Komentarz do Wyjścia 7:8

-9. לאמור…כי ידגר אלכם פרעה, to say: "when Pharaoh will say to you, etc." The reason the Torah adds the word לאמור is to inform us that they had been allowed to inform Pharaoh that they would perform the miracles in G'd's name. Unless such permission had been granted explicitly, they would have been forbidden to reveal this even in response to a question by Pharaoh. We have learned in Yuma 4 that under normal circumstances one is not to reveal the source of one's information unless specifically authorised to do so. The first time the Torah writes לאמור here it is to give Moses and Aaron permission to reveal this information. The Torah repeats the word לאמור once more in order to show that G'd ordered Moses and Aaron to reveal this information.

Another piece of information contained in this verse (according to Torat Kohanim is 1) is that wherever the Torah writes: "to Moses and Aaron," the meaning is that Moses should tell Aaron to carry out G'd's instructions. This piece of exegesis is derived from the very word לאמור here. It means that unlike your impression that G'd spoke to both Moses and Aaron simultaneously, the truth is that G'd spoke to Moses to relay the information to Aaron. The reason that the Torah makes it appear as if G'd had spoken to both of them simultaneously is only to tell us that the commandment performed by Aaron in relaying the information to Pharaoh was equal in importance to Moses having performed his part of the commandment.

פרעה לאמור, תנו לכם מופת, Pharaoh saying: "perform a miracle for your accreditation," the reason the Torah inserts the word לאמור in addition to already having quoted Pharaoh as כי ידבר, was to tell Moses not to volunteer a miracle until Pharaoh actually asked for it. At that point they were to perform the miracle described in our verse. Alternatively, if Pharaoh challenged Moses and Aaron about the authenticity of their mission Moses would also be entitled to tell Aaron to demonstrate the miracle described here.