Charles Ellicott Commentary Hebrews 12:21

"and so fearful was the appearance, [that] Moses said, I exceedingly fear and quake:" — Hebrews 12:21 (ASV)

And so terrible was the sight that. . . .—Better, And (so fearful was the appearance) Moses said, I exceedingly fear and tremble.Deuteronomy 9:19, as it stands in the Greek translation, contains these words in part: I exceedingly fear. However, in that context, they belong to a later time, when Moses was afraid of the anger and hot displeasure of the Lord against the worshippers of the golden calf (Exodus 32:0). Various Jewish traditions speak of the terror of Moses as on Mount Sinai he beheld the wonders of the heavenly world ; but no saying that has been preserved throws additional light on the words before us.