Exodus 34:18-35
"The feast of unleavened bread you shall keep. Seven days you shall eat unleavened bread, as I commanded you, at the time appointed in the month Abib; for in the month Abib you came out from Egypt. All that opens the womb is mine, all your male cattle, the firstlings of cow and sheep. The firstling of an ass you shall redeem with a lamb, or if you will not redeem it you shall break its neck. All the first-born of your sons you shall redeem. And none shall appear before me empty.
"Six days you shall work, but on the seventh day you shall rest; in plowing time and in harvest you shall rest. And you shall observe the feast of weeks, the first fruits of wheat harvest, and the feast of ingathering at the year's end. Three times in the year shall all your males appear before the LORD God, the God of Israel. For I will cast out nations before you, and enlarge your borders; neither shall any man desire your land, when you go up to appear before the LORD your God three times in the year.
"You shall not offer the blood of my sacrifice with leaven; neither shall the sacrifice of the feast of the passover be left until the morning. The first of the first fruits of your ground you shall bring to the house of the LORD your God. You shall not boil a kid in its mother's milk."
And the LORD said to Moses, "Write these words; in accordance with these words I have made a covenant with you and with Israel."
And he was there with the LORD forty days and forty nights; he neither ate bread nor drank water. And he wrote upon the tables the words of the covenant, the ten commandments.
When Moses came down from Mount Sinai, with the two tables 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. And when Aaron and all the people of Israel saw Moses, behold, the skin of his face shone, and they were afraid to come near him. But Moses called to them; and Aaron and all the leaders of the congregation returned to him, and Moses talked with them. And afterward all the people of Israel came near, and he gave them in commandment all that the LORD had spoken with him in Mount Sinai.
And when Moses had finished speaking with them, he put a veil on his face; but whenever Moses went in before the LORD to speak with him, he took the veil off, until he came out; and when he came out, and told the people of Israel what he was commanded, the people of Israel saw the face of Moses, that the skin of Moses' face shone; and Moses would put the veil upon his face again, until he went in to speak with him.