Exodus 34:27-29 American Standard Version (ASV)
27 And Jehovah said unto Moses, Write thou these words: for after the tenor of these words I have made a covenant with thee and with Israel. 28 And he was there with Jehovah forty days and forty nights; he did neither eat bread, nor drink water. And he wrote upon the tables the words of the covenant, the ten [a]commandments.
29 And it came to pass, when Moses came down from mount Sinai with the two tables of the testimony in Moses’ hand, when he came down from the mount, that Moses knew not that the skin of his face [b]shone [c]by reason of his speaking with him.