Exodus 34:27-29

And the LORD said to Moses, “Write these words, for in accordance with these words I have made a covenant with you and with Israel.” So 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. When Moses came down from Mount Sinai, with the two tablets of the testimony in his hand as he came down from the mountain, Moses did not know that the skin of his face shone because he had been talking with God.