Charles Ellicott Commentary 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." — Exodus 4:10 (ASV)

I am not eloquent. — The Hebrew is: No man of words am I. Moses, still reluctant, raises a new objection. He is not gifted with facility of speech. Words do not come readily to him; perhaps, when they come, he has a difficulty in uttering them. According to a Jewish tradition, he was unable to pronounce the labials, b, f, m, p, v. According to his own expressions at the end of the verse, he was heavy or slow of speech, and heavy or slow of tongue.

Neither until now. — The Hebrew is: neither yesterday, nor the day before. It is a Hebrew idiom to make these words cover past time generally. (See below, Exodus 5:7–8, Exodus 5:14; and compare Genesis 31:2, Genesis 31:5, and 2 Samuel 3:17.)

Nor since you have spoken. — Converse with God had not cured his defect of utterance, whatever it was. He remained slow of speech and slow of tongue—unready, i.e., and hesitating.