Exodus 7:2

Thou shalt speak all that I command thee
That is, to Aaron his prophet, whatever the Lord made known to him in a private manner as his will to be done: and Aaron thy brother shall speak unto Pharaoh;
whatsoever should be told him by Moses, as from the Lord: that he send the children of Israel out of his land;
this was the principal thing to be insisted upon; and all that was said or done to him was to bring about this end, the dismission of the children of Israel out of Egypt.