Exodus 34:27

23 Three times a year all your males are to appear before the Lord GOD, the God of Israel.

24 For I will drive out the nations before you and enlarge your borders, and no one will covet your land when you go up three times a year to appear before the LORD your God.

25 Do not offer the blood of a sacrifice to Me along with anything leavened, and do not let any of the sacrifice from the Passover Feast remain until morning.

26 Bring the best of the firstfruits of your soil to the house of the LORD your God. You must not cook a young goat in its mother’s milk.”

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

28 So Moses was there with the LORD forty days and forty nights without eating bread or drinking water. He wrote on the tablets the words of the covenant—the Ten Commandments.

29 And when Moses came down from Mount Sinai with the two tablets of the Testimony in his hands, he was unaware that his face had become radiant from speaking with the LORD.

30 Aaron and all the Israelites looked at Moses, and behold, his face was radiant. And they were afraid to approach him.

31 But Moses called out to them; so Aaron and all the leaders of the congregation returned to him, and Moses spoke to them.

Read all of Exodus 34