(10) But Moses said to the LORD, “Please, O Lord, I have never been a man of words, either in times past or now that You have spoken to Your servant; I am slow of speech and slow of tongue.” (11) And the LORD said to him, “Who gives man speech? Who makes him dumb or deaf, seeing or blind? Is it not I, the LORD? (12) Now go, and I will be with you as you speak and will instruct you what to say.” (13) But he said, “Please, O Lord, make someone else Your agent.” (14) The LORD became angry with Moses, and He said, “There is your brother Aaron the Levite. He, I know, speaks readily. Even now he is setting out to meet you, and he will be happy to see you. (15) You shall speak to him and put the words in his mouth—I will be with you and with him as you speak, and tell both of you what to do— (16) and he shall speak for you to the people. Thus he shall serve as your spokesman, with you playing the role of God to him,

... All this reluctance was because he was unwilling to assume any dignity that would make him superior to his brother Aaron who was older than he and was also a prophet...

כי ידעתיו כי דבר ידבר הוא, for I am well aware that he is an excellent speaker without needing training, וגם הנה הוא יוצא לקראתך וראך ושמח בלבו, and although he is on the way to meet you out of respect for you and your elevation to an even higher status than his own, he will undoubtedly be happy to serve as your interpreter full-heartedly.