This reading is a portion of the Torah reading for Shavuot, which begins this year at sundown May 16.
On the third new moon after the Israelites had gone forth from the land of Egypt, on that very day, they entered the wilderness of Sinai. Having journeyed from Rephidim, they entered the wilderness of Sinai and encamped in the wilderness. Israel encamped there in front of the mountain, and Moses went up to God. The Lord called to him from the mountain, saying, "Thus shall you say to the house of Jacob and declare to the children of Israel: 'You have seen what I did to the Egyptians, how I bore you on eagles' wings and brought you to Me. Now then, if you will obey Me faithfully and keep My covenant, you shall be My treasured possession among all the peoples. Indeed, all the earth is Mine, but you shall be to Me a kingdom of priests and a holy nation.' These are the words that you shall speak to the children of Israel."
Moses came and summoned the elders of the people and put before them all that the Lord had commanded him. All the people answered as one, saying, "All that the Lord has spoken we will do!" And Moses brought back the people's words to the Lord. And the Lord said to Moses, "I will come to you in a thick cloud, in order that the people may hear when I speak with you and so trust you ever after." Then Moses reported the people's words to the Lord, and the Lord said to Moses, "Go to the people and warn them to stay pure today and tomorrow. Let them wash their clothes. Let them be ready for the third day; for on the third day the Lord will come down, in the sight of all the people, on Mount Sinai. You shall set bounds for the people round about, saying, 'Beware of going up the mountain or touching the border of it. Whoever touches the mountain shall be put to death: no hand shall touch him, but he shall be either stoned or shot; beast or man, he shall not live.' When the ram's horn sounds a long blast, they may go up on the mountain."
Moses came down from the mountain to the people and warned the people to stay pure, and they washed their clothes. And he said to the people, "Be ready for the third day: do not go near a woman."