Exodus 4:10

"And Moses said unto Jehovah, Oh Lord, I am not eloquent, neither heretofore, nor since thou hast spoken unto thy servant; for I am slow of speech, and of a slow tongue."

This was the fourth objection raised by Moses against his acceptance of the mission to which God called him, and the very fact of God's ensuing anger with him indicates that there was something very improper with reference to it. God's anger was not actually stated with reference to this objection (that came a moment later), but God did refuse to make any corrective alteration of Moses' speaking ability. Moses also came dangerously close to blaming God for his reluctance in the suggestion that even God's speaking to him had not improved his ability, "nor since thou hast spoken to thy servant!" In his forty years as a shepherd, Moses had found little opportunity to exercise his speaking talents, no doubt having forgotten through neglect much of the Hebrew language which he might not have used for such a long period. Although that might have been Moses' problem, most commentators seem to believe that there was some speech handicap. "According to Jewish tradition, Moses had difficulty in pronouncing the labials b, m, 5ph and p."[12]

"Oh my Lord ..." This is also called an expression of unusual force.[13] It is identical with that which Joseph's brothers used in addressing the steward of Joseph's house (Genesis 43:20). Judah used it when pleading with Joseph to spare Benjamin (Genesis 44:18). Aaron used it when pleading for Miriam (Numbers 12:11). And Joshua thus addressed God when speaking of Ai (Joshua 7:8).