John Calvin Commentary Hebrews 12:25

"See that ye refuse not him that speaketh. For if they escaped not when they refused him that warned [them] on earth, much more [shall not] we [escape] who turn away from him that [warneth] from heaven:" — Hebrews 12:25 (ASV)

See that you refuse not him that speaks, and so on. He uses the same verb as before, when he said that the people pleaded that God should not speak to them; but he means, I think, something else: namely, that we ought not to reject the word destined for us.

He further shows what he intended by the previous comparison: namely, that the severest punishment awaits those who despise the Gospel, since the ancients under the Law did not despise it without punishment. And he pursues the argument from the less to the greater when he says that God or Moses spoke then on earth, but that the same God or Christ now speaks from heaven.

At the same time, I prefer to regard God as the speaker in both instances. And He is said to have spoken on earth because He spoke in a less exalted manner. We should always remember that he refers to the external ministry of the Law, which, when compared with the Gospel, had an earthly character and did not lead people's minds beyond the heavens to perfect wisdom; for though the Law contained the same truth, yet because it was only a training school, perfection could not belong to it.