And it happened when Moses came down from Mount Sinai, with the two tablets of the Covenant in Moses’s hand when he came down from the mountain, that Moses did not know that there was a glow from the skin of his face…Ohr HaHayim explains that Moses was fully aware that there was a glow but he assumed that that the tablets beamed light and he was basking in it. What he did not realize was that it was his face – not the tablets – that was radiating light.