Exodus 4:10

גם מתמול וגו׳ NEITHER FROM YESTERDAY [NOR FROM BEFORE YESTERDAY] — This teaches us that for an entire period of seven days God had been endeavouring to persuade Moses at the thornbush to go on his mission, for the terms מתמול and שלשום and מאז דברך imply three days, and the three-fold גם which is mentioned here point to three extensions of the period, making six in all, and therefore he had now reached the seventh day when he further said to him, (Exodus v. 13) “Send, I pray thee, by the hand of him whom Thou wilt send” — until God became angry with him (Exodus v. 14), and he accepted the mission (cf. Leviticus Rabbah 11:6, and Seder Olam ch. 5). 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, as it is said (I Samuel 2:27) that the man of God spoke to Eli, the high-priest, in God’s name, “Surely I revealed myself unto the house of thy father when they were in Egypt” — thy father means Aaron. Similary in : (Ezekiel 20:5, 7) “And I made myself known unto them in the land of Egypt … and I said unto them, “cast ye away every man the detestable things of his eyes”, and that prophecy was spoken to Aaron (Exodus Rabbah 3:16; and cf. ברייתא דל"ב מדות). כבד פה SLOW OF SPEECH (lit. heavy of mouth) — I speak heavily (with difficulty); old French balbus. (English = stammerer).

וַיֹּ֨אמֶר מֹשֶׁ֣ה אֶל־יְהֹוָה֮ בִּ֣י אֲדֹנָי֒ לֹא֩ אִ֨ישׁ דְּבָרִ֜ים אָנֹ֗כִי גַּ֤ם מִתְּמוֹל֙ גַּ֣ם מִשִּׁלְשֹׁ֔ם גַּ֛ם מֵאָ֥ז דַּבֶּרְךָ֖ אֶל־עַבְדֶּ֑ךָ כִּ֧י כְבַד־פֶּ֛ה וּכְבַ֥ד לָשׁ֖וֹן אָנֹֽכִי׃

And Moshe said to the Lord, O my Lord, I am not an eloquent man, neither yesterday nor the day before, nor since thou hast spoken to thy servant: but I am slow of speech, and of a slow tongue.