John Calvin Commentary Deuteronomy 5:22

"These words Jehovah spake unto all your assembly in the mount out of the midst of the fire, of the cloud, and of the thick darkness, with a great voice: and he added no more. And he wrote them upon two tables of stone, and gave them unto me." — Deuteronomy 5:22 (ASV)

These words the Lord spoke. So that there may be no doubt about the authority of the law, and that it may not be undervalued by the people, Moses reminds them that the presence of God, as He spoke it, was manifested by sure signs. For this was the purpose of the fire, the clouds, and the darkness, by which God’s voice was made evident, so that its source would not be obscure.

He adds that it was a great voice, that is, a voice which had, in an extraordinary manner, reached far and wide. The witnesses he cites are not few; indeed, it was that entire vast multitude, who for the most part would have been more inclined to extinguish God's glory, if it had not been made known there by clear proofs.

In summary, there is no question about who the Lawgiver was, whose majesty was then proclaimed by awe-inspiring wonders and displayed before the eyes of an immense multitude. It will be more convenient to speak elsewhere of the two tables.

When Moses states that God added no more, he means that a perfect rule of life is contained in the Ten Commandments. When their instruction is fully received, the entirety of wisdom is attained, so that the people need not seek to know anything further. Therefore, when God finished speaking, He Himself established the limits of legitimate inquiry.