John Calvin Commentary Exodus 3:6

"Moreover he said, I am the God of thy father, the God of Abraham, the God of Isaac, and the God of Jacob. And Moses hid his face; for he was afraid to look upon God." — Exodus 3:6 (ASV)

I am the God of your father. He does not merely proclaim Himself as some heavenly power, nor claim for Himself only the general name of God; but, recalling His covenant formerly made with the patriarchs, He casts down all idols and false gods and confirms Moses in the true faith.

From this, Moses knew certainly that he had not set his hopes in vain on the God whom Abraham and the other patriarchs had worshipped, and who, by the privilege of adoption, had separated their race from all other nations.

And so that Moses, through the long lapse of time, would not think that what had been passed down about Abraham was obsolete, He expressly asserts that His faithfulness still held true, by calling Himself “the God of his father.”

But since, in presenting the hope of redemption, He renews the memory of His covenant, we infer that it was not obliterated from the heart of Moses. It would have been absurd to speak of something unknown, nor would it have been useful to mention promises of which Moses had no recollection.

Therefore, since the hope of the redemption of the chosen people depended on the covenant which God had formerly made with the patriarchs, He shows that He had not been trusted in vain, because His commitment would not be ineffectual.

It was not so much a sign of reverence as of terror that Moses covered his face. Yet we must take both feelings into account: that he felt sudden alarm at the sight of God and voluntarily adored His majesty.

It was necessary that his mind should be affected and impressed with reverential feelings, so that he might be more ready to obey.

We read in Isaiah (Isaiah 6:2) that even the angels veil their faces because they cannot bear the infinite glory of God. It is no wonder, then, that a mortal man dared not look upon Him.

The name of God is associated with the visible appearance in which His majesty was concealed.