John Chrysostom
"See that you do not refuse Him who is speaking," that is, do not disobey.
"For if they did not escape when they refused Him who spoke on earth."
Whom does he mean here? It seems to me that he means Moses. The sense of his words is this: if they did not escape punishment when they disobeyed the one who commanded on earth, how can we disobey the One who commands from heaven?
Here he does not mean that there was one lawgiver there and another here. Certainly not. He does not point to one there and another here, but says that the One who speaks from heaven is fearful.
Though the same One is present both there and here, He is especially fearful as He speaks here. The Apostle speaks of a difference not in persons, but in gifts.
From where is this clear? From his following words: "If they did not escape when they refused Him who spoke on earth, much more shall we not escape if we turn away from Him who speaks from heaven."