Albert Barnes Commentary Exodus 6:13

"And Jehovah spake unto Moses and unto Aaron, and gave them a charge unto the children of Israel, and unto Pharaoh king of Egypt, to bring the children of Israel out of the land of Egypt." — Exodus 6:13 (ASV)

To Moses and to Aaron - The final and formal charge to the two brothers is given, as might be expected, before the plagues are proclaimed. With this verse begins a new section of the history.