Exodus 34:27-29

27Then Adonai said to Moses, “Write these words, for based on these words I have cut a covenant with you and with Israel.”

28So he stayed there with Adonai for 40 days and 40 nights, and he did not eat bread or drink water. He wrote on the tablets the words of the covenant: the Ten Words.

29Now it happened, when Moses came down from Mount Sinai with the two tablets of the Testimony in his hand when he came down from the mountain, that Moses did not know that the skin of his face was radiant, because God had spoken with him.