Exodus 34:27-29 World English Bible (WEB)
27 Yahweh said to Moses, “Write you these words: for in accordance with these words I have made a covenant with you and with Israel.”
28 He was there with Yahweh forty days and forty nights; he neither ate bread, nor drank water. He wrote on the tablets the words of the covenant, the ten commandments.
29 When Moses came down from Mount Sinai with the two tablets of the testimony in Moses’ hand, when he came down from the mountain, Moses didn’t know that the skin of his face shone by reason of his speaking with him.