The Reformed Episcopal Church Book of Common Prayer has these two morning readings: Exodus 4:1-23 and Hebrews 10:1-18.
Now that Moses has heard the plan he has questions: “What if they will not believe me or listen to what I say? For they may say, ‘The Lord has not appeared to you.” (verse 1). Does this sound like us when the Lord asks us to tell others about Him?
The Lord gives Moses three signs:
The staff that becomes a serpent (verses 2-5)
Moses hand that becomes leprous. (verses 6-7)
Water that turns to blood (verses 8-9).
Now the Lord has proven again His power to Moses but again Moses resists the call and protests further by saying that he is not a good speaker. (verses 10-13).
Finally, in apparent frustration, the Lord tells Moses his brother Aaron will speak for him. However, in verses 16-17 an interesting statement is made by the Lord indicating His intent with Aaron: “Moreover, he shall speak for you to the people; and he will be as a mouth for you and you will be as God to him. 17 You shall take in your hand this staff, with which you shall perform the signs.”
It appears the Lord has set Moses and Aaron in a God and mediator role with implications for the future. Moses is the authority even possessing the power to bring forth the signs while Aaron represents Moses to the people. This explains why from Aaron would come the Priesthood under the law of Moses. Priests being Ambassadors of God as they Minister the righteousness of the Lord through His Word and Offerings.
Now the team is set so Moses takes care of personal matters, telling his father in law he is returning to Egypt and taking his wife and sons with him.
The Lord concludes (verses 19-23) by giving Moses hope that those who knew him and sought his life are dead and the His plan is motivated by the fact that He sees Israel as His first born son. Looking back you can see that the Lord dealt with Israel corporately as a single entity teaching them and us about Himself and what He expects from us.
Hebrews tells us again the difference between the offerings in the Law of Moses and the offering of Christ Himself and while His first born son Israel needed redeeming His first begotten Son was the One intended to redeem Israel.