Adam Clarke on Exodus 33:20

No man see me, and live - The splendor would be insufferable to man; he only, whose mortality is swallowed up of life, can see God as he is. See 1Jn 3:2. From some disguised relation of the circumstances mentioned here, the fable of Jupiter and Semele was formed; she is reported to have entreated Jupiter to show her his glory, who was at first very reluctant, knowing that it would be fatal to her; but at last, yielding to her importunity, he discovered his divine majesty, and she was consumed by his presence. This story is told by Ovid in his Metamorphoses, book iii., table iii., 5.