Exodus 34:27-29

27The Lord also said to Moses, “Write down these words, for I have made a covenant with you and with Israel based on these words.”

28Moses was there with the Lord forty days and forty nights; he did not eat food or drink water. He wrote the Ten Commandments, the words of the covenant, on the tablets.

29As Moses descended from Mount Sinai — with the two tablets of the testimony in his hands as he descended the mountain — he did not realize that the skin of his face shone as a result of his speaking with the Lord.