Exodus 20 :18

And all the people saw the thunderings, etc. - They had witnessed all these awful things before, (see Exodus 19:16), but here they seem to have been repeated; probably at the end of each command, there was a peal of thunder, a blast of the trumpet, and a gleam of lightning, to impress their hearts the more deeply with a due sense of the Divine Majesty, of the holiness of the law which was now delivered, and of the fearful consequences of disobedience. This had the desired effect; the people were impressed with a deep religious fear and a terror of God's judgments; acknowledged themselves perfectly satisfied with the discoveries God had made of himself; and requested that Moses might be constituted the mediator between God and them, as they were not able to bear these tremendous discoveries of the Divine Majesty. "Speak thou with us, and we will hear; but let not God speak with us, lest we die;" Exodus 20:19. This teaches us the absolute necessity of that great Mediator between God and man, Christ Jesus, as no man can come unto the Father but by him.

Compare Deuteronomy 5:22-31. Aaron Exodus 19:24 on this occasion accompanied Moses in drawing near to the thick darkness.

Exodus 20:22 to Exodus 23:33 is a series of laws which we may identify with what was written by Moses in the book called the book of the covenant, and read by him in the audience of the people Exodus 24:7.

The document cannot be regarded as a strictly systematic whole. Portions of it were probably traditional rules handed down from the patriarchs, and retained by the Israelites in Egypt.

20:18 They removed and stood afar off - Before God began to speak, they were thrusting forward to gaze, but now they were effectually cured of their presumption, and taught to keep their distance.