Exodus 34:27-29

27Then the Lord said to Moses, “Write these words, for according to the tenor of these words I have made a covenant with you and with Israel.”

28So he was there with the Lord forty days and forty nights; he neither ate bread nor drank water. And He wrote on the tablets the words of the covenant, the Ten Commandments.

29Now it was so, when Moses came down from Mount Sinai (and the two tablets of the Testimony were in Moses’ hand when he came down from the mountain), that Moses did not know that the skin of his face shone while he talked with Him.