פרשת שמות תשכ"א - סירובו של משה לשליחות

And he said: ‘Oh Lord, send, I pray Thee, by the hand of him whom Thou wilt send.’

ביד תשלח signifies by the hand of him whom Thou art accustomed to send; viz., Aaron (Exodus Rabbah 3:16). Another explanation is: by the hand of some other person whom Thou wilt be pleased to send — for in the end “I” shall not bring them into the land of Palestine nor shall “I” become their deliverer in the future — and You have many messengers! (Pirkei DeRabbi Eliezer 40)

...In the hand of who you usually send and this is Ahron. Another opinion, with another hand of who you want them to be sent for my destiny is not to lead them into the land of Israel and to be their redeemer in the future. You have a lot of other messengers, these are the words of Rashi. And Onkelos says, send it in the hand of someone who is appropriate to go (like a general or ambassador), meaning, send with someone who can speak eloquently who is appropriate for this honorable task. And don't send someone who cannot speak well, who you will have to talk for. Because it is not a way of respect to send someone who has problems speaking, no ones going to listen when you speak to the king and it will be disgust in their eyes. And what is correct in my eyes: Send please in the hand of anywhich you can send. Because there is not a person in this world that will not be more appropriate than me for this mission. And the reason for Moshe's refusal in this is his humbleness. He would have never found it in his heart to rise up and speak to the king and be glorified. It is not in is character to say Hashem sent me and not to take the Jewish people out of Egypt and not to be the king.

And he said: ‘Oh Lord, send, I pray Thee, by the hand of him whom Thou wilt send.’

And Moses went and returned to Jethro his father-in-law, and said unto him: ‘Let me go, I pray thee, and unto my brethren that are in Egypt, and see whether they be yet alive.’ And Jethro said to Moses: ‘Go in peace.’